/* pngread.c - read a PNG file * * Copyright (c) 2018-2025 Cosmin Truta * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson * Copyright (c) 1996-1997 Andreas Dilger * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. * * This code is released under the libpng license. * For conditions of distribution and use, see the disclaimer * and license in png.h * * This file contains routines that an application calls directly to * read a PNG file or stream.
*/
#include"pngpriv.h" #ifdefined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED) # include <errno.h> #endif
if (png_ptr != NULL)
{
png_ptr->mode = PNG_IS_READ_STRUCT;
/* Added in libpng-1.6.0; this can be used to detect a read structure if * required (it will be zero in a write structure.)
*/ # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE; # endif
/* In stable builds only warn if an application error can be completely * handled.
*/ # if PNG_RELEASE_BUILD
png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN; # endif # endif
/* TODO: delay this, it can be done in png_init_io (if the app doesn't * do it itself) avoiding setting the default function if it is not * required.
*/
png_set_read_fn(png_ptr, NULL, NULL);
}
return png_ptr;
}
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED /* Read the information before the actual image data. This has been * changed in v0.90 to allow reading a file that already has the magic * bytes read from the stream. You can tell libpng how many bytes have * been read from the beginning of the stream (up to the maximum of 8) * via png_set_sig_bytes(), and we will only check the remaining bytes * here. The application can then have access to the signature bytes we * read if it is determined that this isn't a valid PNG file.
*/ void PNGAPI
png_read_info(png_structrp png_ptr, png_inforp info_ptr)
{ #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED int keep; #endif
png_debug(1, "in png_read_info");
if (png_ptr == NULL || info_ptr == NULL) return;
/* Read and check the PNG file signature. */
png_read_sig(png_ptr, info_ptr);
/* IDAT logic needs to happen here to simplify getting the two flags * right.
*/ if (chunk_name == png_IDAT)
{ if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
png_chunk_error(png_ptr, "Missing IHDR before IDAT");
/* This should be a binary subdivision search or a hash for * matching the chunk name rather than a linear search.
*/ if (chunk_name == png_IHDR)
png_handle_IHDR(png_ptr, info_ptr, length);
have_chunk_after_DAT = 0; for (;;)
{
png_uint_32 length = png_read_chunk_header(png_ptr);
if (png_ptr->chunk_name == png_IDAT)
{ /* discard trailing IDATs for the first frame */ if (have_chunk_after_DAT != 0 || png_ptr->num_frames_read > 1)
png_error(png_ptr, "png_read_frame_head(): out of place IDAT");
png_crc_finish(png_ptr, length);
}
/* New in 1.6.0 this avoids the bug of doing the initializations twice */ else
png_app_error(png_ptr, "png_read_update_info/png_start_read_image: duplicate call");
}
}
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED /* Initialize palette, background, etc, after transformations * are set, but before any reading takes place. This allows * the user to obtain a gamma-corrected palette, for example. * If the user doesn't call this, we will do it ourselves.
*/ void PNGAPI
png_start_read_image(png_structrp png_ptr)
{
png_debug(1, "in png_start_read_image");
if (png_ptr != NULL)
{ if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
png_read_start_row(png_ptr);
/* New in 1.6.0 this avoids the bug of doing the initializations twice */ else
png_app_error(png_ptr, "png_start_read_image/png_read_update_info: duplicate call");
}
} #endif/* SEQUENTIAL_READ */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED #ifdef PNG_MNG_FEATURES_SUPPORTED /* Undoes intrapixel differencing, * NOTE: this is apparently only supported in the 'sequential' reader.
*/ staticvoid
png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_read_intrapixel");
if (
(row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
{ int bytes_per_pixel;
png_uint_32 row_width = row_info->width;
if (row_info->bit_depth == 8)
{
png_bytep rp;
png_uint_32 i;
if (row_info->color_type == PNG_COLOR_TYPE_RGB)
bytes_per_pixel = 3;
png_debug2(1, "in png_read_row (row %lu, pass %d)",
(unsignedlong)png_ptr->row_number, png_ptr->pass);
/* png_read_start_row sets the information (in particular iwidth) for this * interlace pass.
*/ if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
png_read_start_row(png_ptr);
/* 1.5.6: row_info moved out of png_struct to a local here. */
row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
row_info.color_type = png_ptr->color_type;
row_info.bit_depth = png_ptr->bit_depth;
row_info.channels = png_ptr->channels;
row_info.pixel_depth = png_ptr->pixel_depth;
row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
#ifdef PNG_WARNINGS_SUPPORTED if (png_ptr->row_number == 0 && png_ptr->pass == 0)
{ /* Check for transforms that have been set but were defined out */ #ifdefined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED) if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED) if ((png_ptr->transformations & PNG_FILLER) != 0)
png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
!defined(PNG_READ_PACKSWAP_SUPPORTED) if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED) if ((png_ptr->transformations & PNG_PACK) != 0)
png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) if ((png_ptr->transformations & PNG_SHIFT) != 0)
png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED) if ((png_ptr->transformations & PNG_BGR) != 0)
png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined"); #endif
#ifdefined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED) if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined"); #endif
} #endif/* WARNINGS */
#ifdef PNG_READ_INTERLACING_SUPPORTED /* If interlaced and we do not need a new row, combine row and return. * Notice that the pixels we have from previous rows have been transformed * already; we can only combine like with like (transformed or * untransformed) and, because of the libpng API for interlaced images, this * means we must transform before de-interlacing.
*/ if (png_ptr->interlaced != 0 &&
(png_ptr->transformations & PNG_INTERLACE) != 0)
{ switch (png_ptr->pass)
{ case 0: if (png_ptr->row_number & 0x07)
{ if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
case 1: if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
{ if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
case 2: if ((png_ptr->row_number & 0x07) != 4)
{ if (dsp_row != NULL && (png_ptr->row_number & 4))
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
case 3: if ((png_ptr->row_number & 3) || png_ptr->width < 3)
{ if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
case 4: if ((png_ptr->row_number & 3) != 2)
{ if (dsp_row != NULL && (png_ptr->row_number & 2))
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
case 5: if ((png_ptr->row_number & 1) || png_ptr->width < 2)
{ if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, 1/*display*/);
png_read_finish_row(png_ptr); return;
} break;
default: case 6: if ((png_ptr->row_number & 1) == 0)
{
png_read_finish_row(png_ptr); return;
} break;
}
} #endif
if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
png_error(png_ptr, "Invalid attempt to read row data");
/* Fill the row with IDAT data: */
png_ptr->row_buf[0]=255; /* to force error if no data was found */
png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
/* libpng 1.5.6: the following line was copying png_ptr->rowbytes before * 1.5.6, while the buffer really is this big in current versions of libpng * it may not be in the future, so this was changed just to copy the * interlaced count:
*/
memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
/* The transformed pixel depth should match the depth now in row_info. */ if (png_ptr->transformed_pixel_depth == 0)
{
png_ptr->transformed_pixel_depth = row_info.pixel_depth; if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
png_error(png_ptr, "sequential row overflow");
}
#ifdef PNG_READ_INTERLACING_SUPPORTED /* Expand interlaced rows to full size */ if (png_ptr->interlaced != 0 &&
(png_ptr->transformations & PNG_INTERLACE) != 0)
{ if (png_ptr->pass < 6)
png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
png_ptr->transformations);
if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, 1/*display*/);
if (row != NULL)
png_combine_row(png_ptr, row, 0/*row*/);
}
else #endif
{ if (row != NULL)
png_combine_row(png_ptr, row, -1/*ignored*/);
if (dsp_row != NULL)
png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
}
png_read_finish_row(png_ptr);
if (png_ptr->read_row_fn != NULL)
(*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
} #endif/* SEQUENTIAL_READ */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED /* Read one or more rows of image data. If the image is interlaced, * and png_set_interlace_handling() has been called, the rows need to * contain the contents of the rows from the previous pass. If the * image has alpha or transparency, and png_handle_alpha()[*] has been * called, the rows contents must be initialized to the contents of the * screen. * * "row" holds the actual image, and pixels are placed in it * as they arrive. If the image is displayed after each pass, it will * appear to "sparkle" in. "display_row" can be used to display a * "chunky" progressive image, with finer detail added as it becomes * available. If you do not want this "chunky" display, you may pass * NULL for display_row. If you do not want the sparkle display, and * you have not called png_handle_alpha(), you may pass NULL for rows. * If you have called png_handle_alpha(), and the image has either an * alpha channel or a transparency chunk, you must provide a buffer for * rows. In this case, you do not have to provide a display_row buffer * also, but you may. If the image is not interlaced, or if you have * not called png_set_interlace_handling(), the display_row buffer will * be ignored, so pass NULL to it. * * [*] png_handle_alpha() does not exist yet, as of this version of libpng
*/
rp = row;
dp = display_row; if (rp != NULL && dp != NULL) for (i = 0; i < num_rows; i++)
{
png_bytep rptr = *rp++;
png_bytep dptr = *dp++;
png_read_row(png_ptr, rptr, dptr);
}
elseif (rp != NULL) for (i = 0; i < num_rows; i++)
{
png_bytep rptr = *rp;
png_read_row(png_ptr, rptr, NULL);
rp++;
}
elseif (dp != NULL) for (i = 0; i < num_rows; i++)
{
png_bytep dptr = *dp;
png_read_row(png_ptr, NULL, dptr);
dp++;
}
} #endif/* SEQUENTIAL_READ */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED /* Read the entire image. If the image has an alpha channel or a tRNS * chunk, and you have called png_handle_alpha()[*], you will need to * initialize the image to the current image that PNG will be overlaying. * We set the num_rows again here, in case it was incorrectly set in * png_read_start_row() by a call to png_read_update_info() or * png_start_read_image() if png_set_interlace_handling() wasn't called * prior to either of these functions like it should have been. You can * only call this function once. If you desire to have an image for * each pass of a interlaced image, use png_read_rows() instead. * * [*] png_handle_alpha() does not exist yet, as of this version of libpng
*/ void PNGAPI
png_read_image(png_structrp png_ptr, png_bytepp image)
{
png_uint_32 i, image_height; int pass, j;
png_bytepp rp;
png_debug(1, "in png_read_image");
if (png_ptr == NULL) return;
#ifdef PNG_READ_INTERLACING_SUPPORTED if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
{
pass = png_set_interlace_handling(png_ptr); /* And make sure transforms are initialized. */
png_start_read_image(png_ptr);
} else
{ if (png_ptr->interlaced != 0 &&
(png_ptr->transformations & PNG_INTERLACE) == 0)
{ /* Caller called png_start_read_image or png_read_update_info without * first turning on the PNG_INTERLACE transform. We can fix this here, * but the caller should do it!
*/
png_warning(png_ptr, "Interlace handling should be turned on when " "using png_read_image"); /* Make sure this is set correctly */
png_ptr->num_rows = png_ptr->height;
}
/* Obtain the pass number, which also turns on the PNG_INTERLACE flag in * the above error case.
*/
pass = png_set_interlace_handling(png_ptr);
} #else if (png_ptr->interlaced)
png_error(png_ptr, "Cannot read interlaced image -- interlace handler disabled");
pass = 1; #endif
image_height=png_ptr->height;
for (j = 0; j < pass; j++)
{
rp = image; for (i = 0; i < image_height; i++)
{
png_read_row(png_ptr, *rp, NULL);
rp++;
}
}
} #endif/* SEQUENTIAL_READ */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED /* Read the end of the PNG file. Will not read past the end of the * file, will verify the end is accurate, and will read any comments * or time information at the end of the file, if info is not NULL.
*/ void PNGAPI
png_read_end(png_structrp png_ptr, png_inforp info_ptr)
{ #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED int keep; #endif
png_debug(1, "in png_read_end");
if (png_ptr == NULL) return;
/* If png_read_end is called in the middle of reading the rows there may * still be pending IDAT data and an owned zstream. Deal with this here.
*/ #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0) #endif
png_read_finish_IDAT(png_ptr);
#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED /* Report invalid palette index; added at libng-1.5.10 */ if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
png_ptr->num_palette_max >= png_ptr->num_palette)
png_benign_error(png_ptr, "Read palette index exceeding num_palette"); #endif
do
{
png_uint_32 length = png_read_chunk_header(png_ptr);
png_uint_32 chunk_name = png_ptr->chunk_name;
if (chunk_name != png_IDAT)
png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
if (chunk_name == png_IEND)
png_handle_IEND(png_ptr, info_ptr, length);
elseif (chunk_name == png_IDAT)
{ /* Zero length IDATs are legal after the last IDAT has been * read, but not after other chunks have been read. 1.6 does not * always read all the deflate data; specifically it cannot be relied * upon to read the Adler32 at the end. If it doesn't ignore IDAT * chunks which are longer than zero as well:
*/ if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
|| (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
png_benign_error(png_ptr, "..Too many IDATs found");
/* NOTE: the 'setjmp' buffer may still be allocated and the memory and error * callbacks are still set at this point. They are required to complete the * destruction of the png_struct itself.
*/
}
/* Free all memory used by the read */ void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
png_infopp end_info_ptr_ptr)
{
png_structrp png_ptr = NULL;
png_debug(1, "in png_destroy_read_struct");
if (png_ptr_ptr != NULL)
png_ptr = *png_ptr_ptr;
if (png_ptr == NULL) return;
/* libpng 1.6.0: use the API to destroy info structs to ensure consistent * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API. * The extra was, apparently, unnecessary yet this hides memory leak bugs.
*/
png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
png_destroy_info_struct(png_ptr, info_ptr_ptr);
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED #ifdef PNG_INFO_IMAGE_SUPPORTED void PNGAPI
png_read_png(png_structrp png_ptr, png_inforp info_ptr, int transforms, voidp params)
{
png_debug(1, "in png_read_png");
if (png_ptr == NULL || info_ptr == NULL) return;
/* png_read_info() gives us all of the information from the * PNG file before the first IDAT (image data chunk).
*/
png_read_info(png_ptr, info_ptr); if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
png_error(png_ptr, "Image is too high to process with png_read_png()");
/* -------------- image transformations start here ------------------- */ /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM * is not implemented. This will only happen in de-configured (non-default) * libpng builds. The results can be unexpected - png_read_png may return * short or mal-formed rows because the transform is skipped.
*/
/* Tell libpng to strip 16-bit/color files down to 8 bits per color.
*/ if ((transforms & PNG_TRANSFORM_SCALE_16) != 0) /* Added at libpng-1.5.4. "strip_16" produces the same result that it * did in earlier versions, while "scale_16" is now more accurate.
*/ #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
png_set_scale_16(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported"); #endif
/* If both SCALE and STRIP are required pngrtran will effectively cancel the * latter by doing SCALE first. This is ok and allows apps not to check for * which is supported to get the right answer.
*/ if ((transforms & PNG_TRANSFORM_STRIP_16) != 0) #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
png_set_strip_16(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported"); #endif
/* Strip alpha bytes from the input data without combining with * the background (not recommended).
*/ if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0) #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
png_set_strip_alpha(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported"); #endif
/* Extract multiple pixels with bit depths of 1, 2, or 4 from a single * byte into separate bytes (useful for paletted and grayscale images).
*/ if ((transforms & PNG_TRANSFORM_PACKING) != 0) #ifdef PNG_READ_PACK_SUPPORTED
png_set_packing(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported"); #endif
/* Change the order of packed pixels to least significant bit first * (not useful if you are using png_set_packing).
*/ if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0) #ifdef PNG_READ_PACKSWAP_SUPPORTED
png_set_packswap(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported"); #endif
/* Expand paletted colors into true RGB triplets * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel * Expand paletted or RGB images with transparency to full alpha * channels so the data will be available as RGBA quartets.
*/ if ((transforms & PNG_TRANSFORM_EXPAND) != 0) #ifdef PNG_READ_EXPAND_SUPPORTED
png_set_expand(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported"); #endif
/* We don't handle background color or gamma transformation or quantizing.
*/
/* Invert monochrome files to have 0 as white and 1 as black
*/ if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0) #ifdef PNG_READ_INVERT_SUPPORTED
png_set_invert_mono(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported"); #endif
/* If you want to shift the pixel values from the range [0,255] or * [0,65535] to the original [0,7] or [0,31], or whatever range the * colors were originally in:
*/ if ((transforms & PNG_TRANSFORM_SHIFT) != 0) #ifdef PNG_READ_SHIFT_SUPPORTED if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
png_set_shift(png_ptr, &info_ptr->sig_bit); #else
png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported"); #endif
/* Flip the RGB pixels to BGR (or RGBA to BGRA) */ if ((transforms & PNG_TRANSFORM_BGR) != 0) #ifdef PNG_READ_BGR_SUPPORTED
png_set_bgr(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported"); #endif
/* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0) #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
png_set_swap_alpha(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported"); #endif
/* Swap bytes of 16-bit files to least significant byte first */ if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0) #ifdef PNG_READ_SWAP_SUPPORTED
png_set_swap(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported"); #endif
/* Added at libpng-1.2.41 */ /* Invert the alpha channel from opacity to transparency */ if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0) #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
png_set_invert_alpha(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported"); #endif
/* Added at libpng-1.2.41 */ /* Expand grayscale image to RGB */ if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0) #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
png_set_gray_to_rgb(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported"); #endif
/* Added at libpng-1.5.4 */ if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0) #ifdef PNG_READ_EXPAND_16_SUPPORTED
png_set_expand_16(png_ptr); #else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported"); #endif
/* We don't handle adding filler bytes */
/* We use png_read_image and rely on that for interlace handling, but we also * call png_read_update_info therefore must turn on interlace handling now:
*/
(void)png_set_interlace_handling(png_ptr);
/* Optional call to gamma correct and add the background to the palette * and update info structure. REQUIRED if you are expecting libpng to * update the palette for you (i.e., you selected such a transform above).
*/
png_read_update_info(png_ptr, info_ptr);
/* -------------- image transformations end here ------------------- */
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED /* SIMPLIFIED READ * * This code currently relies on the sequential reader, though it could easily * be made to work with the progressive one.
*/ /* Arguments to png_image_finish_read: */
/* Encoding of PNG data (used by the color-map code) */ # define P_NOTSET 0 /* File encoding not yet known */ # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */ # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */ # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */ # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
/* Color-map processing: after libpng has run on the PNG image further * processing may be needed to convert the data to color-map indices.
*/ #define PNG_CMAP_NONE 0 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */ #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */ #define PNG_CMAP_RGB 3 /* Process RGB data */ #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
/* The following document where the background is for each processing case. */ #define PNG_CMAP_NONE_BACKGROUND 256 #define PNG_CMAP_GA_BACKGROUND 231 #define PNG_CMAP_TRANS_BACKGROUND 254 #define PNG_CMAP_RGB_BACKGROUND 256 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
typedefstruct
{ /* Arguments: */
png_imagep image;
png_voidp buffer;
png_int_32 row_stride;
png_voidp colormap;
png_const_colorp background; /* Local variables: */
png_voidp local_row;
png_voidp first_row;
ptrdiff_t row_bytes; /* step between rows */ int file_encoding; /* E_ values above */
png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */ int colormap_processing; /* PNG_CMAP_ values above */
} png_image_read_control;
/* Do all the *safe* initialization - 'safe' means that png_error won't be * called, so setting up the jmp_buf is not required. This means that anything * called from here must *not* call png_malloc - it has to call png_malloc_warn * instead so that control is returned safely back to this routine.
*/ staticint
png_image_read_init(png_imagep image)
{ if (image->opaque == NULL)
{
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
png_safe_error, png_safe_warning);
/* And set the rest of the structure to NULL to ensure that the various * fields are consistent.
*/
memset(image, 0, (sizeof *image));
image->version = PNG_IMAGE_VERSION;
if (png_ptr != NULL)
{
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr != NULL)
{
png_controlp control = png_voidcast(png_controlp,
png_malloc_warn(png_ptr, (sizeof *control)));
if (control != NULL)
{
memset(control, 0, (sizeof *control));
/* Error clean up */
png_destroy_info_struct(png_ptr, &info_ptr);
}
png_destroy_read_struct(&png_ptr, NULL, NULL);
}
return png_image_error(image, "png_image_read: out of memory");
}
return png_image_error(image, "png_image_read: opaque pointer not NULL");
}
/* Utility to find the base format of a PNG file from a png_struct. */ static png_uint_32
png_image_format(png_structrp png_ptr)
{
png_uint_32 format = 0;
if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
format |= PNG_FORMAT_FLAG_COLOR;
if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
format |= PNG_FORMAT_FLAG_ALPHA;
/* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS * sets the png_struct fields; that's all we are interested in here. The * precise interaction with an app call to png_set_tRNS and PNG file reading * is unclear.
*/ elseif (png_ptr->num_trans > 0)
format |= PNG_FORMAT_FLAG_ALPHA;
if (png_ptr->bit_depth == 16)
format |= PNG_FORMAT_FLAG_LINEAR;
if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
format |= PNG_FORMAT_FLAG_COLORMAP;
return format;
}
/* Is the given gamma significantly different from sRGB? The test is the same * one used in pngrtran.c when deciding whether to do gamma correction. The * arithmetic optimizes the division by using the fact that the inverse of the * file sRGB gamma is 2.2
*/ staticint
png_gamma_not_sRGB(png_fixed_point g)
{ if (g < PNG_FP_1)
{ /* An uninitialized gamma is assumed to be sRGB for the simplified API. */ if (g == 0) return 0;
/* Do the main body of a 'png_image_begin_read' function; read the PNG file * header and fill in all the information. This is executed in a safe context, * unlike the init routine above.
*/ staticint
png_image_read_header(png_voidp argument)
{
png_imagep image = png_voidcast(png_imagep, argument);
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
/* Do this the fast way; just read directly out of png_struct. */
image->width = png_ptr->width;
image->height = png_ptr->height;
{
png_uint_32 format = png_image_format(png_ptr);
image->format = format;
#ifdef PNG_COLORSPACE_SUPPORTED /* Does the colorspace match sRGB? If there is no color endpoint * (colorant) information assume yes, otherwise require the * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the * colorspace has been determined to be invalid ignore it.
*/ if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
& (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB; #endif
}
/* We need the maximum number of entries regardless of the format the * application sets here.
*/
{
png_uint_32 cmap_entries;
case PNG_COLOR_TYPE_PALETTE:
cmap_entries = (png_uint_32)png_ptr->num_palette; break;
default:
cmap_entries = 256; break;
}
if (cmap_entries > 256)
cmap_entries = 256;
image->colormap_entries = cmap_entries;
}
return 1;
}
#ifdef PNG_STDIO_SUPPORTED int PNGAPI
png_image_begin_read_from_stdio(png_imagep image, FILE* file)
{ if (image != NULL && image->version == PNG_IMAGE_VERSION)
{ if (file != NULL)
{ if (png_image_read_init(image) != 0)
{ /* This is slightly evil, but png_init_io doesn't do anything other * than this and we haven't changed the standard IO functions so * this saves a 'safe' function.
*/
image->opaque->png_ptr->io_ptr = file; return png_safe_execute(image, png_image_read_header, image);
}
}
png_error(png_ptr, "read beyond end of data");
}
}
png_error(png_ptr, "invalid memory read");
}
}
int PNGAPI png_image_begin_read_from_memory(png_imagep image,
png_const_voidp memory, size_t size)
{ if (image != NULL && image->version == PNG_IMAGE_VERSION)
{ if (memory != NULL && size > 0)
{ if (png_image_read_init(image) != 0)
{ /* Now set the IO functions to read from the memory buffer and * store it into io_ptr. Again do this in-place to avoid calling a * libpng function that requires error handling.
*/
image->opaque->memory = png_voidcast(png_const_bytep, memory);
image->opaque->size = size;
image->opaque->png_ptr->io_ptr = image;
image->opaque->png_ptr->read_data_fn = png_image_memory_read;
/* Utility function to skip chunks that are not used by the simplified image * read functions and an appropriate macro to call it.
*/ #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED staticvoid
png_image_skip_unused_chunks(png_structrp png_ptr)
{ /* Prepare the reader to ignore all recognized chunks whose data will not * be used, i.e., all chunks recognized by libpng except for those * involved in basic image reading: * * IHDR, PLTE, IDAT, IEND * * Or image data handling: * * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT. * * This provides a small performance improvement and eliminates any * potential vulnerability to security problems in the unused chunks. * * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored * too. This allows the simplified API to be compiled without iCCP support, * however if the support is there the chunk is still checked to detect * errors (which are unfortunately quite common.)
*/
{ staticconst png_byte chunks_to_process[] = {
98, 75, 71, 68, '\0', /* bKGD */
99, 72, 82, 77, '\0', /* cHRM */
103, 65, 77, 65, '\0', /* gAMA */ # ifdef PNG_READ_iCCP_SUPPORTED
105, 67, 67, 80, '\0', /* iCCP */ # endif
115, 66, 73, 84, '\0', /* sBIT */
115, 82, 71, 66, '\0', /* sRGB */
};
/* Ignore unknown chunks and all other chunks except for the * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
*/
png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
NULL, -1);
/* But do not ignore image data handling chunks */
png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
}
}
/* The following macro gives the exact rounded answer for all values in the * range 0..255 (it actually divides by 51.2, but the rounding still generates * the correct numbers 0..5
*/ #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
/* Utility functions to make particular color-maps */ staticvoid
set_file_encoding(png_image_read_control *display)
{
png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma; if (png_gamma_significant(g) != 0)
{ if (png_gamma_not_sRGB(g) != 0)
{
display->file_encoding = P_FILE;
display->gamma_to_linear = png_reciprocal(g);
}
else
display->file_encoding = P_sRGB;
}
else
display->file_encoding = P_LINEAR8;
}
staticunsignedint
decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
{ if (encoding == P_FILE) /* double check */
encoding = display->file_encoding;
if (encoding == P_NOTSET) /* must be the file encoding */
{
set_file_encoding(display);
encoding = display->file_encoding;
}
switch (encoding)
{ case P_FILE:
value = png_gamma_16bit_correct(value*257, display->gamma_to_linear); break;
case P_sRGB:
value = png_sRGB_table[value]; break;
static png_uint_32
png_colormap_compose(png_image_read_control *display,
png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
png_uint_32 background, int encoding)
{ /* The file value is composed on the background, the background has the given * encoding and so does the result, the file is encoded with P_FILE and the * file and alpha are 8-bit values. The (output) encoding will always be * P_LINEAR or P_sRGB.
*/
png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
png_uint_32 b = decode_gamma(display, background, encoding);
/* The alpha is always an 8-bit value (it comes from the palette), the value * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
*/
f = f * alpha + b * (255-alpha);
if (encoding == P_LINEAR)
{ /* Scale to 65535; divide by 255, approximately (in fact this is extremely * accurate, it divides by 255.00000005937181414556, with no overflow.)
*/
f *= 257; /* Now scaled by 65535 */
f += f >> 16;
f = (f+32768) >> 16;
}
else/* P_sRGB */
f = PNG_sRGB_FROM_LINEAR(f);
return f;
}
/* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must * be 8-bit.
*/ staticvoid
png_create_colormap_entry(png_image_read_control *display,
png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
png_uint_32 alpha, int encoding)
{
png_imagep image = display->image; int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB; int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
(red != green || green != blue);
if (ip > 255)
png_error(image->opaque->png_ptr, "color-map index out of range");
/* Update the cache with whether the file gamma is significantly different * from sRGB.
*/ if (encoding == P_FILE)
{ if (display->file_encoding == P_NOTSET)
set_file_encoding(display);
/* Note that the cached value may be P_FILE too, but if it is then the * gamma_to_linear member has been set.
*/
encoding = display->file_encoding;
}
if (encoding == P_FILE)
{
png_fixed_point g = display->gamma_to_linear;
red = png_gamma_16bit_correct(red*257, g);
green = png_gamma_16bit_correct(green*257, g);
blue = png_gamma_16bit_correct(blue*257, g);
else
{
red = PNG_sRGB_FROM_LINEAR(red * 255);
green = PNG_sRGB_FROM_LINEAR(green * 255);
blue = PNG_sRGB_FROM_LINEAR(blue * 255);
encoding = P_sRGB;
}
}
elseif (encoding == P_LINEAR8)
{ /* This encoding occurs quite frequently in test cases because PngSuite * includes a gAMA 1.0 chunk with most images.
*/
red *= 257;
green *= 257;
blue *= 257;
alpha *= 257;
encoding = P_LINEAR;
}
elseif (encoding == P_sRGB &&
(convert_to_Y != 0 || output_encoding == P_LINEAR))
{ /* The values are 8-bit sRGB values, but must be converted to 16-bit * linear.
*/
red = png_sRGB_table[red];
green = png_sRGB_table[green];
blue = png_sRGB_table[blue];
alpha *= 257;
encoding = P_LINEAR;
}
/* This is set if the color isn't gray but the output is. */ if (encoding == P_LINEAR)
{ if (convert_to_Y != 0)
{ /* NOTE: these values are copied from png_do_rgb_to_gray */
png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
(png_uint_32)2366 * blue;
if (output_encoding == P_LINEAR)
y = (y + 16384) >> 15;
else
{ /* y is scaled by 32768, we need it scaled by 255: */
y = (y + 128) >> 8;
y *= 255;
y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
alpha = PNG_DIV257(alpha);
encoding = P_sRGB;
}
blue = red = green = y;
}
elseif (output_encoding == P_sRGB)
{
red = PNG_sRGB_FROM_LINEAR(red * 255);
green = PNG_sRGB_FROM_LINEAR(green * 255);
blue = PNG_sRGB_FROM_LINEAR(blue * 255);
alpha = PNG_DIV257(alpha);
encoding = P_sRGB;
}
}
if (encoding != output_encoding)
png_error(image->opaque->png_ptr, "bad encoding (internal error)");
if (output_encoding == P_LINEAR)
{
png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
/* The linear 16-bit values must be pre-multiplied by the alpha channel * value, if less than 65535 (this is, effectively, composite on black * if the alpha channel is removed.)
*/ switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
{ case 4:
entry[afirst ? 0 : 3] = (png_uint_16)alpha; /* FALLTHROUGH */
case 3: if (alpha < 65535)
{ if (alpha > 0)
{
blue = (blue * alpha + 32767U)/65535U;
green = (green * alpha + 32767U)/65535U;
red = (red * alpha + 32767U)/65535U;
}
else
red = green = blue = 0;
}
entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
entry[afirst + 1] = (png_uint_16)green;
entry[afirst + bgr] = (png_uint_16)red; break;
case 2:
entry[1 ^ afirst] = (png_uint_16)alpha; /* FALLTHROUGH */
case 1: if (alpha < 65535)
{ if (alpha > 0)
green = (green * alpha + 32767U)/65535U;
else
green = 0;
}
entry[afirst] = (png_uint_16)green; break;
staticint
make_ga_colormap(png_image_read_control *display)
{ unsignedint i, a;
/* Alpha is retained, the output will be a color-map with entries * selected by six levels of alpha. One transparent entry, 6 gray * levels for all the intermediate alpha values, leaving 230 entries * for the opaque grays. The color-map entries are the six values * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the * relevant entry. * * if (alpha > 229) // opaque * { * // The 231 entries are selected to make the math below work: * base = 0; * entry = (231 * gray + 128) >> 8; * } * else if (alpha < 26) // transparent * { * base = 231; * entry = 0; * } * else // partially opaque * { * base = 226 + 6 * PNG_DIV51(alpha); * entry = PNG_DIV51(gray); * }
*/
i = 0; while (i < 231)
{ unsignedint gray = (i * 256 + 115) / 231;
png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
}
/* 255 is used here for the component values for consistency with the code * that undoes premultiplication in pngwrite.c.
*/
png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
/* Return a palette index to the above palette given three 8-bit sRGB values. */ #define PNG_RGB_INDEX(r,g,b) \
((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
unsignedint cmap_entries; unsignedint output_processing; /* Output processing option */ unsignedint data_encoding = P_NOTSET; /* Encoding libpng must produce */
/* Background information; the background color and the index of this color * in the color-map if it exists (else 256).
*/ unsignedint background_index = 256;
png_uint_32 back_r, back_g, back_b;
/* Flags to accumulate things that need to be done to the input. */ int expand_tRNS = 0;
/* Exclude the NYI feature of compositing onto a color-mapped buffer; it is * very difficult to do, the results look awful, and it is difficult to see * what possible use it is because the application can't control the * color-map.
*/ if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
png_ptr->num_trans > 0) /* alpha in input */ &&
((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
{ if (output_encoding == P_LINEAR) /* compose on black */
back_b = back_g = back_r = 0;
elseif (display->background == NULL /* no way to remove it */)
png_error(png_ptr, "background color must be supplied to remove alpha/transparency");
/* Get a copy of the background color (this avoids repeating the checks * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the * output format.
*/ else
{
back_g = display->background->green; if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
{
back_r = display->background->red;
back_b = display->background->blue;
} else
back_b = back_r = back_g;
}
}
/* Default the input file gamma if required - this is necessary because * libpng assumes that if no gamma information is present the data is in the * output format, but the simplified API deduces the gamma from the input * format.
*/ if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
{ /* Do this directly, not using the png_colorspace functions, to ensure * that it happens even if the colorspace is invalid (though probably if * it is the setting will be ignored) Note that the same thing can be * achieved at the application interface with png_set_gAMA.
*/ if (png_ptr->bit_depth == 16 &&
(image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
/* Decide what to do based on the PNG color type of the input data. The * utility function png_create_colormap_entry deals with most aspects of the * output transformations; this code works out how to produce bytes of * color-map entries from the original format.
*/ switch (png_ptr->color_type)
{ case PNG_COLOR_TYPE_GRAY: if (png_ptr->bit_depth <= 8)
{ /* There at most 256 colors in the output, regardless of * transparency.
*/ unsignedint step, i, val, trans = 256/*ignore*/, back_alpha = 0;
cmap_entries = 1U << png_ptr->bit_depth; if (cmap_entries > image->colormap_entries)
png_error(png_ptr, "gray[8] color-map: too few entries");
/* If there is a tRNS chunk then this either selects a transparent * value or, if the output has no alpha, the background color.
*/ if (png_ptr->num_trans > 0)
{
trans = png_ptr->trans_color.gray;
/* png_create_colormap_entry just takes an RGBA and writes the * corresponding color-map entry using the format from 'image', * including the required conversion to sRGB or linear as * appropriate. The input values are always either sRGB (if the * gamma correction flag is 0) or 0..255 scaled file encoded values * (if the function must gamma correct them).
*/ for (i=val=0; i<cmap_entries; ++i, val += step)
{ /* 'i' is a file value. While this will result in duplicated * entries for 8-bit non-sRGB encoded files it is necessary to * have non-gamma corrected values to do tRNS handling.
*/ if (i != trans)
png_create_colormap_entry(display, i, val, val, val, 255,
P_FILE/*8-bit with file gamma*/);
/* Else this entry is transparent. The colors don't matter if * there is an alpha channel (back_alpha == 0), but it does no * harm to pass them in; the values are not set above so this * passes in white. * * NOTE: this preserves the full precision of the application * supplied background color when it is used.
*/ else
png_create_colormap_entry(display, i, back_r, back_g, back_b,
back_alpha, output_encoding);
}
/* We need libpng to preserve the original encoding. */
data_encoding = P_FILE;
/* The rows from libpng, while technically gray values, are now also * color-map indices; however, they may need to be expanded to 1 * byte per pixel. This is what png_set_packing does (i.e., it * unpacks the bit values into bytes.)
*/ if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
}
else/* bit depth is 16 */
{ /* The 16-bit input values can be converted directly to 8-bit gamma * encoded values; however, if a tRNS chunk is present 257 color-map * entries are required. This means that the extra entry requires * special processing; add an alpha channel, sacrifice gray level * 254 and convert transparent (alpha==0) entries to that. * * Use libpng to chop the data to 8 bits. Convert it to sRGB at the * same time to minimize quality loss. If a tRNS chunk is present * this means libpng must handle it too; otherwise it is impossible * to do the exact match on the 16-bit value. * * If the output has no alpha channel *and* the background color is * gray then it is possible to let libpng handle the substitution by * ensuring that the corresponding gray level matches the background * color exactly.
*/
data_encoding = P_sRGB;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray[16] color-map: too few entries");
if (png_ptr->num_trans > 0)
{ unsignedint back_alpha;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
back_alpha = 0;
else
{ if (back_r == back_g && back_g == back_b)
{ /* Background is gray; no special processing will be * required.
*/
png_color_16 c;
png_uint_32 gray = back_g;
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(gray * 255);
/* And make sure the corresponding palette entry * matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the * sRGB value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
/* NOTE: does this work without expanding tRNS to alpha? * It should be the color->gray case below apparently * doesn't.
*/
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
/* output_processing means that the libpng-processed row will be * 8-bit GA and it has to be processing to single byte color-map * values. Entry 254 is replaced by either a completely * transparent entry or by the background color at full * precision (and the background color is not a simple gray * level in this case.)
*/
expand_tRNS = 1;
output_processing = PNG_CMAP_TRANS;
background_index = 254;
/* And set (overwrite) color-map entry 254 to the actual * background color at full precision.
*/
png_create_colormap_entry(display, 254, back_r, back_g, back_b,
back_alpha, output_encoding);
}
else
output_processing = PNG_CMAP_NONE;
} break;
case PNG_COLOR_TYPE_GRAY_ALPHA: /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum * of 65536 combinations. If, however, the alpha channel is to be * removed there are only 256 possibilities if the background is gray. * (Otherwise there is a subset of the 65536 possibilities defined by * the triangle between black, white and the background color.) * * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to * worry about tRNS matching - tRNS is ignored if there is an alpha * channel.
*/
data_encoding = P_sRGB;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{ if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray+alpha color-map: too few entries");
else/* alpha is removed */
{ /* Alpha must be removed as the PNG data is processed when the * background is a color because the G and A channels are * independent and the vector addition (non-parallel vectors) is a * 2-D problem. * * This can be reduced to the same algorithm as above by making a * colormap containing gray levels (for the opaque grays), a * background entry (for a transparent pixel) and a set of four six * level color values, one set for each intermediate alpha value. * See the comments in make_ga_colormap for how this works in the * per-pixel processing. * * If the background is gray, however, we only need a 256 entry gray * level color map. It is sufficient to make the entry generated * for the background color be exactly the color specified.
*/ if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
(back_r == back_g && back_g == back_b))
{ /* Background is gray; no special processing will be required. */
png_color_16 c;
png_uint_32 gray = back_g;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray-alpha color-map: too few entries");
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(gray * 255);
/* And make sure the corresponding palette entry matches. */
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the sRGB * value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_NONE;
}
else
{
png_uint_32 i, a;
/* This is the same as png_make_ga_colormap, above, except that * the entries are all opaque.
*/ if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "ga-alpha color-map: too few entries");
i = 0; while (i < 231)
{
png_uint_32 gray = (i * 256 + 115) / 231;
png_create_colormap_entry(display, i++, gray, gray, gray,
255, P_sRGB);
}
/* NOTE: this preserves the full precision of the application * background color.
*/
background_index = i;
png_create_colormap_entry(display, i++, back_r, back_g, back_b, #ifdef __COVERITY__ /* Coverity claims that output_encoding * cannot be 2 (P_LINEAR) here.
*/ #else
output_encoding == P_LINEAR ? 65535U : 255U, #endif
output_encoding);
/* For non-opaque input composite on the sRGB background - this * requires inverting the encoding for each component. The input * is still converted to the sRGB encoding because this is a * reasonable approximate to the logarithmic curve of human * visual sensitivity, at least over the narrow range which PNG * represents. Consequently 'G' is always sRGB encoded, while * 'A' is linear. We need the linear background colors.
*/ if (output_encoding == P_sRGB) /* else already linear */
{ /* This may produce a value not exactly matching the * background, but that's ok because these numbers are only * used when alpha != 0
*/
back_r = png_sRGB_table[back_r];
back_g = png_sRGB_table[back_g];
back_b = png_sRGB_table[back_b];
}
for (a=1; a<5; ++a)
{ unsignedint g;
/* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled * by an 8-bit alpha value (0..255).
*/
png_uint_32 alpha = 51 * a;
png_uint_32 back_rx = (255-alpha) * back_r;
png_uint_32 back_gx = (255-alpha) * back_g;
png_uint_32 back_bx = (255-alpha) * back_b;
case PNG_COLOR_TYPE_RGB: case PNG_COLOR_TYPE_RGB_ALPHA: /* Exclude the case where the output is gray; we can always handle this * with the cases above.
*/ if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
{ /* The color-map will be grayscale, so we may as well convert the * input RGB values to a simple grayscale and use the grayscale * code above. * * NOTE: calling this apparently damages the recognition of the * transparent color in background color handling; call * png_set_tRNS_to_alpha before png_set_background_fixed.
*/
png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
-1);
data_encoding = P_sRGB;
/* The output will now be one or two 8-bit gray or gray+alpha * channels. The more complex case arises when the input has alpha.
*/ if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
(output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{ /* Both input and output have an alpha channel, so no background * processing is required; just map the GA bytes to the right * color-map entry.
*/
expand_tRNS = 1;
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[ga] color-map: too few entries");
else
{ /* Either the input or the output has no alpha channel, so there * will be no non-opaque pixels in the color-map; it will just be * grayscale.
*/ if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[gray] color-map: too few entries");
/* Ideally this code would use libpng to do the gamma correction, * but if an input alpha channel is to be removed we will hit the * libpng bug in gamma+compose+rgb-to-gray (the double gamma * correction bug). Fix this by dropping the gamma correction in * this case and doing it in the palette; this will result in * duplicate palette entries, but that's better than the * alternative of double gamma correction.
*/ if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
{
cmap_entries = (unsignedint)make_gray_file_colormap(display);
data_encoding = P_FILE;
}
/* But if the input has alpha or transparency it must be removed
*/ if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{
png_color_16 c;
png_uint_32 gray = back_g;
/* We need to ensure that the application background exists in * the colormap and that completely transparent pixels map to * it. Achieve this simply by ensuring that the entry * selected for the background really is the background color.
*/ if (data_encoding == P_FILE) /* from the fixup above */
{ /* The app supplied a gray which is in output_encoding, we * need to convert it to a value of the input (P_FILE) * encoding then set this palette entry to the required * output encoding.
*/ if (output_encoding == P_sRGB)
gray = png_sRGB_table[gray]; /* now P_LINEAR */
gray = PNG_DIV257(png_gamma_16bit_correct(gray,
png_ptr->colorspace.gamma)); /* now P_FILE */
/* And make sure the corresponding palette entry contains * exactly the required sRGB value.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, output_encoding);
}
/* And make sure the corresponding palette entry matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, P_LINEAR);
}
/* The background passed to libpng, however, must be the * output (normally sRGB) value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
/* NOTE: the following is apparently a bug in libpng. Without * it the transparent color recognition in * png_set_background_fixed seems to go wrong.
*/
expand_tRNS = 1;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
}
output_processing = PNG_CMAP_NONE;
}
}
else/* output is color */
{ /* We could use png_quantize here so long as there is no transparent * color or alpha; png_quantize ignores alpha. Easier overall just * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube. * Consequently we always want libpng to produce sRGB data.
*/
data_encoding = P_sRGB;
/* Is there any transparency or alpha? */ if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{ /* Is there alpha in the output too? If so all four channels are * processed into a special RGB cube with alpha support.
*/ if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
png_uint_32 r;
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb+alpha color-map: too few entries");
else
{ /* Alpha/transparency must be removed. The background must * exist in the color map (achieved by setting adding it after * the 666 color-map). If the standard processing code will * pick up this entry automatically that's all that is * required; libpng can be called to do the background * processing.
*/ unsignedint sample_size =
PNG_IMAGE_SAMPLE_SIZE(output_format);
png_uint_32 r, g, b; /* sRGB background */
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb-alpha color-map: too few entries");
if (output_encoding == P_LINEAR)
{
r = PNG_sRGB_FROM_LINEAR(back_r * 255);
g = PNG_sRGB_FROM_LINEAR(back_g * 255);
b = PNG_sRGB_FROM_LINEAR(back_b * 255);
}
else
{
r = back_r;
g = back_g;
b = back_g;
}
/* Compare the newly-created color-map entry with the one the * PNG_CMAP_RGB algorithm will use. If the two entries don't * match, add the new one and set this as the background * index.
*/ if (memcmp((png_const_bytep)display->colormap +
sample_size * cmap_entries,
(png_const_bytep)display->colormap +
sample_size * PNG_RGB_INDEX(r,g,b),
sample_size) != 0)
{ /* The background color must be added. */
background_index = cmap_entries++;
/* Add 27 r,g,b entries each with created by composing with * the background at alpha 0.5.
*/ for (r=0; r<256; r = (r << 1) | 0x7f)
{ for (g=0; g<256; g = (g << 1) | 0x7f)
{ /* This generates components with the values 0, 127 * and 255
*/ for (b=0; b<256; b = (b << 1) | 0x7f)
png_create_colormap_entry(display, cmap_entries++,
png_colormap_compose(display, r, P_sRGB, 128,
back_r, output_encoding),
png_colormap_compose(display, g, P_sRGB, 128,
back_g, output_encoding),
png_colormap_compose(display, b, P_sRGB, 128,
back_b, output_encoding),
0/*unused*/, output_encoding);
}
}
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_RGB;
}
}
}
else/* no alpha or transparency in the input */
{ /* Alpha in the output is irrelevant, simply map the opaque input * pixels to the 6x6x6 color-map.
*/ if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb color-map: too few entries");
case PNG_COLOR_TYPE_PALETTE: /* It's already got a color-map. It may be necessary to eliminate the * tRNS entries though.
*/
{ unsignedint num_trans = png_ptr->num_trans;
png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
png_const_colorp colormap = png_ptr->palette; int do_background = trans != NULL &&
(output_format & PNG_FORMAT_FLAG_ALPHA) == 0; unsignedint i;
/* Just in case: */ if (trans == NULL)
num_trans = 0;
output_processing = PNG_CMAP_NONE;
data_encoding = P_FILE; /* Don't change from color-map indices */
cmap_entries = (unsignedint)png_ptr->num_palette; if (cmap_entries > 256)
cmap_entries = 256;
if (cmap_entries > (unsignedint)image->colormap_entries)
png_error(png_ptr, "palette color-map: too few entries");
for (i=0; i < cmap_entries; ++i)
{ if (do_background != 0 && i < num_trans && trans[i] < 255)
{ if (trans[i] == 0)
png_create_colormap_entry(display, i, back_r, back_g,
back_b, 0, output_encoding);
else
{ /* Must compose the PNG file color in the color-map entry * on the sRGB color in 'back'.
*/
png_create_colormap_entry(display, i,
png_colormap_compose(display, colormap[i].red,
P_FILE, trans[i], back_r, output_encoding),
png_colormap_compose(display, colormap[i].green,
P_FILE, trans[i], back_g, output_encoding),
png_colormap_compose(display, colormap[i].blue,
P_FILE, trans[i], back_b, output_encoding),
output_encoding == P_LINEAR ? trans[i] * 257U :
trans[i],
output_encoding);
}
}
else
png_create_colormap_entry(display, i, colormap[i].red,
colormap[i].green, colormap[i].blue,
i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
}
/* The PNG data may have indices packed in fewer than 8 bits, it * must be expanded if so.
*/ if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
} break;
default:
png_error(png_ptr, "invalid PNG color type"); /*NOT REACHED*/
}
/* Now deal with the output processing */ if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
(png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
png_set_tRNS_to_alpha(png_ptr);
switch (data_encoding)
{ case P_sRGB: /* Change to 8-bit sRGB */
png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB); /* FALLTHROUGH */
case P_FILE: if (png_ptr->bit_depth > 8)
png_set_scale_16(png_ptr); break;
/* Double check using the recorded background index */ switch (output_processing)
{ case PNG_CMAP_NONE: if (background_index != PNG_CMAP_NONE_BACKGROUND) goto bad_background; break;
case PNG_CMAP_GA: if (background_index != PNG_CMAP_GA_BACKGROUND) goto bad_background; break;
case PNG_CMAP_TRANS: if (background_index >= cmap_entries ||
background_index != PNG_CMAP_TRANS_BACKGROUND) goto bad_background; break;
case PNG_CMAP_RGB: if (background_index != PNG_CMAP_RGB_BACKGROUND) goto bad_background; break;
case PNG_CMAP_RGB_ALPHA: if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND) goto bad_background; break;
/* The final part of the color-map read called from png_image_finish_read. */ staticint
png_image_read_and_map(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr; int passes;
/* Called when the libpng data must be transformed into the color-mapped * form. There is a local row buffer in display->local and this routine must * do the interlace handling.
*/ switch (png_ptr->interlaced)
{ case PNG_INTERLACE_NONE:
passes = 1; break;
case PNG_INTERLACE_ADAM7:
passes = PNG_INTERLACE_ADAM7_PASSES; break;
for (; y<height; y += stepy)
{
png_bytep inrow = png_voidcast(png_bytep, display->local_row);
png_bytep outrow = first_row + y * step_row;
png_const_bytep end_row = outrow + width;
/* Read read the libpng data into the temporary buffer. */
png_read_row(png_ptr, inrow, NULL);
/* Now process the row according to the processing option, note * that the caller verifies that the format of the libpng output * data is as required.
*/
outrow += startx; switch (proc)
{ case PNG_CMAP_GA: for (; outrow < end_row; outrow += stepx)
{ /* The data is always in the PNG order */ unsignedint gray = *inrow++; unsignedint alpha = *inrow++; unsignedint entry;
/* NOTE: this code is copied as a comment in * make_ga_colormap above. Please update the * comment if you change this code!
*/ if (alpha > 229) /* opaque */
{
entry = (231 * gray + 128) >> 8;
} elseif (alpha < 26) /* transparent */
{
entry = 231;
} else/* partially opaque */
{
entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
}
*outrow = (png_byte)entry;
} break;
case PNG_CMAP_TRANS: for (; outrow < end_row; outrow += stepx)
{
png_byte gray = *inrow++;
png_byte alpha = *inrow++;
if (alpha == 0)
*outrow = PNG_CMAP_TRANS_BACKGROUND;
else
{ /* Likewise there are three entries for each of r, g * and b. We could select the entry by popcount on * the top two bits on those architectures that * support it, this is what the code below does, * crudely.
*/ unsignedint back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
/* Here are how the values map: * * 0x00 .. 0x3f -> 0 * 0x40 .. 0xbf -> 1 * 0xc0 .. 0xff -> 2 * * So, as above with the explicit alpha checks, the * breakpoints are at 64 and 196.
*/ if (inrow[0] & 0x80) back_i += 9; /* red */ if (inrow[0] & 0x40) back_i += 9; if (inrow[0] & 0x80) back_i += 3; /* green */ if (inrow[0] & 0x40) back_i += 3; if (inrow[0] & 0x80) back_i += 1; /* blue */ if (inrow[0] & 0x40) back_i += 1;
/* Update the 'info' structure and make sure the result is as required; first * make sure to turn on the interlace handling if it will be required * (because it can't be turned on *after* the call to png_read_update_info!)
*/ if (display->colormap_processing == PNG_CMAP_NONE)
passes = png_set_interlace_handling(png_ptr);
png_read_update_info(png_ptr, info_ptr);
/* The expected output can be deduced from the colormap_processing option. */ switch (display->colormap_processing)
{ case PNG_CMAP_NONE: /* Output must be one channel and one byte per pixel, the output * encoding can be anything.
*/ if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
info_ptr->bit_depth == 8) break;
goto bad_output;
case PNG_CMAP_TRANS: case PNG_CMAP_GA: /* Output must be two channels and the 'G' one must be sRGB, the latter * can be checked with an exact number because it should have been set * to this number above!
*/ if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
info_ptr->bit_depth == 8 &&
png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
image->colormap_entries == 256) break;
goto bad_output;
case PNG_CMAP_RGB: /* Output must be 8-bit sRGB encoded RGB */ if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
info_ptr->bit_depth == 8 &&
png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
image->colormap_entries == 216) break;
goto bad_output;
case PNG_CMAP_RGB_ALPHA: /* Output must be 8-bit sRGB encoded RGBA */ if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
info_ptr->bit_depth == 8 &&
png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
image->colormap_entries == 244 /* 216 + 1 + 27 */) break;
/* Now read the rows. Do this here if it is possible to read directly into * the output buffer, otherwise allocate a local row buffer of the maximum * size libpng requires and call the relevant processing routine safely.
*/
{
png_voidp first_row = display->buffer;
ptrdiff_t row_bytes = display->row_stride;
/* The following expression is designed to work correctly whether it gives * a signed or an unsigned result.
*/ if (row_bytes < 0)
{ char *ptr = png_voidcast(char*, first_row);
ptr += (image->height-1) * (-row_bytes);
first_row = png_voidcast(png_voidp, ptr);
}
/* Now do the composition on each pixel in this row. */
outrow += startx; for (; outrow < end_row; outrow += stepx)
{
png_byte alpha = inrow[channels];
if (alpha > 0) /* else no change to the output */
{ unsignedint c;
for (c=0; c<channels; ++c)
{
png_uint_32 component = inrow[c];
if (alpha < 255) /* else just use component */
{ /* This is PNG_OPTIMIZED_ALPHA, the component value * is a linear 8-bit value. Combine this with the * current outrow[c] value which is sRGB encoded. * Arithmetic here is 16-bits to preserve the output * values correctly.
*/
component *= 257*255; /* =65535 */
component += (255-alpha)*png_sRGB_table[outrow[c]];
/* So 'component' is scaled by 255*65535 and is * therefore appropriate for the sRGB to linear * conversion table.
*/
component = PNG_sRGB_FROM_LINEAR(component);
}
/* The do_local_background case; called when all the following transforms are to * be done: * * PNG_RGB_TO_GRAY * PNG_COMPOSITE * PNG_GAMMA * * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and * PNG_COMPOSITE code performs gamma correction, so we get double gamma * correction. The fix-up is to prevent the PNG_COMPOSITE operation from * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha * row and handles the removal or pre-multiplication of the alpha channel.
*/ staticint
png_image_read_background(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
png_uint_32 height = image->height;
png_uint_32 width = image->width; int pass, passes;
/* Double check the convoluted logic below. We expect to get here with * libpng doing rgb to gray and gamma correction but background processing * left to the png_image_read_background function. The rows libpng produce * might be 8 or 16-bit but should always have two channels; gray plus alpha.
*/ if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
png_error(png_ptr, "lost rgb to gray");
if ((png_ptr->transformations & PNG_COMPOSE) != 0)
png_error(png_ptr, "unexpected compose");
if (png_get_channels(png_ptr, info_ptr) != 2)
png_error(png_ptr, "lost/gained channels");
/* Expect the 8-bit case to always remove the alpha channel */ if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
(image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
png_error(png_ptr, "unexpected 8-bit transformation");
switch (png_ptr->interlaced)
{ case PNG_INTERLACE_NONE:
passes = 1; break;
case PNG_INTERLACE_ADAM7:
passes = PNG_INTERLACE_ADAM7_PASSES; break;
/* Use direct access to info_ptr here because otherwise the simplified API * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is * checking the value after libpng expansions, not the original value in the * PNG.
*/ switch (info_ptr->bit_depth)
{ case 8: /* 8-bit sRGB gray values with an alpha channel; the alpha channel is * to be removed by composing on a background: either the row if * display->background is NULL or display->background->green if not. * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
*/
{
png_bytep first_row = png_voidcast(png_bytep, display->first_row);
ptrdiff_t step_row = display->row_bytes;
if (display->background == NULL)
{ for (; y<height; y += stepy)
{
png_bytep inrow = png_voidcast(png_bytep,
display->local_row);
png_bytep outrow = first_row + y * step_row;
png_const_bytep end_row = outrow + width;
/* Read the row, which is packed: */
png_read_row(png_ptr, inrow, NULL);
/* Now do the composition on each pixel in this row. */
outrow += startx; for (; outrow < end_row; outrow += stepx)
{
png_byte alpha = inrow[1];
if (alpha > 0) /* else no change to the output */
{
png_uint_32 component = inrow[0];
if (alpha < 255) /* else just use component */
{ /* Since PNG_OPTIMIZED_ALPHA was not set it is * necessary to invert the sRGB transfer * function and multiply the alpha out.
*/
component = png_sRGB_table[component] * alpha;
component += png_sRGB_table[outrow[0]] *
(255-alpha);
component = PNG_sRGB_FROM_LINEAR(component);
}
case 16: /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must * still be done and, maybe, the alpha channel removed. This code also * handles the alpha-first option.
*/
{
png_uint_16p first_row = png_voidcast(png_uint_16p,
display->first_row); /* The division by two is safe because the caller passed in a * stride which was multiplied by 2 (below) to get row_bytes.
*/
ptrdiff_t step_row = display->row_bytes / 2; unsignedint preserve_alpha = (image->format &
PNG_FORMAT_FLAG_ALPHA) != 0; unsignedint outchannels = 1U+preserve_alpha; int swap_alpha = 0;
/* The 'x' start and step are adjusted to output components here.
*/ if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
{ /* The row may be empty for a short image: */ if (PNG_PASS_COLS(width, pass) == 0) continue;
/* Read the row, which is packed: */
png_read_row(png_ptr, png_voidcast(png_bytep,
display->local_row), NULL);
inrow = png_voidcast(png_const_uint_16p, display->local_row);
/* Now do the pre-multiplication on each pixel in this row.
*/
outrow += startx; for (; outrow < end_row; outrow += stepx)
{
png_uint_32 component = inrow[0];
png_uint_16 alpha = inrow[1];
if (alpha > 0) /* else 0 */
{ if (alpha < 65535) /* else just use component */
{
component *= alpha;
component += 32767;
component /= 65535;
}
}
#ifdef __GNUC__ default:
png_error(png_ptr, "unexpected bit depth"); #endif
}
return 1;
}
/* The guts of png_image_finish_read as a png_safe_execute callback. */ staticint
png_image_read_direct(png_voidp argument)
{
png_image_read_control *display = png_voidcast(png_image_read_control*,
argument);
png_imagep image = display->image;
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
png_uint_32 format = image->format; int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0; int do_local_compose = 0; int do_local_background = 0; /* to avoid double gamma correction bug */ int passes = 0;
/* Add transforms to ensure the correct output format is produced then check * that the required implementation support is there. Always expand; always * need 8 bits minimum, no palette and expanded tRNS.
*/
png_set_expand(png_ptr);
/* Now check the format to see if it was modified. */
{
png_uint_32 base_format = png_image_format(png_ptr) &
~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
png_uint_32 change = format ^ base_format;
png_fixed_point output_gamma; int mode; /* alpha mode */
/* Do this first so that we have a record if rgb to gray is happening. */ if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
{ /* gray<->color transformation required. */ if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
png_set_gray_to_rgb(png_ptr);
else
{ /* libpng can't do both rgb to gray and * background/pre-multiplication if there is also significant gamma * correction, because both operations require linear colors and * the code only supports one transform doing the gamma correction. * Handle this by doing the pre-multiplication or background * operation in this code, if necessary. * * TODO: fix this by rewriting pngrtran.c (!) * * For the moment (given that fixing this in pngrtran.c is an * enormous change) 'do_local_background' is used to indicate that * the problem exists.
*/ if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
do_local_background = 1/*maybe*/;
/* Call png_set_alpha_mode to set the default for the input gamma; the * output gamma is set by a second call below.
*/
png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
}
if (linear != 0)
{ /* If there *is* an alpha channel in the input it must be multiplied * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
*/ if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
mode = PNG_ALPHA_STANDARD; /* associated alpha */
/* If 'do_local_background' is set check for the presence of gamma * correction; this is part of the work-round for the libpng bug * described above. * * TODO: fix libpng and remove this.
*/ if (do_local_background != 0)
{
png_fixed_point gtest;
/* This is 'png_gamma_threshold' from pngrtran.c; the test used for * gamma correction, the screen gamma hasn't been set on png_struct * yet; it's set below. png_struct::gamma, however, is set to the * final value.
*/ if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
do_local_background = 0;
/* If the bit-depth changes then handle that here. */ if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
{ if (linear != 0 /*16-bit output*/)
png_set_expand_16(png_ptr);
else/* 8-bit output */
png_set_scale_16(png_ptr);
change &= ~PNG_FORMAT_FLAG_LINEAR;
}
/* Now the background/alpha channel changes. */ if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
{ /* Removing an alpha channel requires composition for the 8-bit * formats; for the 16-bit it is already done, above, by the * pre-multiplication and the channel just needs to be stripped.
*/ if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{ /* If RGB->gray is happening the alpha channel must be left and the * operation completed locally. * * TODO: fix libpng and remove this.
*/ if (do_local_background != 0)
do_local_background = 2/*required*/;
/* 16-bit output: just remove the channel */ elseif (linear != 0) /* compose on black (well, pre-multiply) */
png_set_strip_alpha(png_ptr);
/* 8-bit output: do an appropriate compose */ elseif (display->background != NULL)
{
png_color_16 c;
/* This is always an 8-bit sRGB value, using the 'green' channel * for gray is much better than calculating the luminance here; * we can get off-by-one errors in that calculation relative to * the app expectations and that will show up in transparent * pixels.
*/
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
}
else/* compose on row: implemented below. */
{
do_local_compose = 1; /* This leaves the alpha channel in the output, so it has to be * removed by the code below. Set the encoding to the 'OPTIMIZE' * one so the code only has to hack on the pixels that require * composition.
*/
mode = PNG_ALPHA_OPTIMIZED;
}
}
else/* output needs an alpha channel */
{ /* This is tricky because it happens before the swap operation has * been accomplished; however, the swap does *not* swap the added * alpha channel (weird API), so it must be added in the correct * place.
*/
png_uint_32 filler; /* opaque filler */ int where;
if (linear != 0)
filler = 65535;
else
filler = 255;
#ifdef PNG_FORMAT_AFIRST_SUPPORTED if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
{
where = PNG_FILLER_BEFORE;
change &= ~PNG_FORMAT_FLAG_AFIRST;
}
else #endif
where = PNG_FILLER_AFTER;
png_set_add_alpha(png_ptr, filler, where);
}
/* This stops the (irrelevant) call to swap_alpha below. */
change &= ~PNG_FORMAT_FLAG_ALPHA;
}
/* Now set the alpha mode correctly; this is always done, even if there is * no alpha channel in either the input or the output because it correctly * sets the output gamma.
*/
png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
# ifdef PNG_FORMAT_BGR_SUPPORTED if ((change & PNG_FORMAT_FLAG_BGR) != 0)
{ /* Check only the output format; PNG is never BGR; don't do this if * the output is gray, but fix up the 'format' value in that case.
*/ if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
png_set_bgr(png_ptr);
else
format &= ~PNG_FORMAT_FLAG_BGR;
change &= ~PNG_FORMAT_FLAG_BGR;
} # endif
# ifdef PNG_FORMAT_AFIRST_SUPPORTED if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
{ /* Only relevant if there is an alpha channel - it's particularly * important to handle this correctly because do_local_compose may * be set above and then libpng will keep the alpha channel for this * code to remove.
*/ if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
{ /* Disable this if doing a local background, * TODO: remove this when local background is no longer required.
*/ if (do_local_background != 2)
png_set_swap_alpha(png_ptr);
}
else
format &= ~PNG_FORMAT_FLAG_AFIRST;
change &= ~PNG_FORMAT_FLAG_AFIRST;
} # endif
/* If the *output* is 16-bit then we need to check for a byte-swap on this * architecture.
*/ if (linear != 0)
{
png_uint_16 le = 0x0001;
if ((*(png_const_bytep) & le) != 0)
png_set_swap(png_ptr);
}
/* If change is not now 0 some transformation is missing - error out. */ if (change != 0)
png_error(png_ptr, "png_read_image: unsupported transformation");
}
PNG_SKIP_CHUNKS(png_ptr);
/* Update the 'info' structure and make sure the result is as required; first * make sure to turn on the interlace handling if it will be required * (because it can't be turned on *after* the call to png_read_update_info!) * * TODO: remove the do_local_background fixup below.
*/ if (do_local_compose == 0 && do_local_background != 2)
passes = png_set_interlace_handling(png_ptr);
png_read_update_info(png_ptr, info_ptr);
{
png_uint_32 info_format = 0;
if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
info_format |= PNG_FORMAT_FLAG_COLOR;
if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
{ /* do_local_compose removes this channel below. */ if (do_local_compose == 0)
{ /* do_local_background does the same if required. */ if (do_local_background != 2 ||
(format & PNG_FORMAT_FLAG_ALPHA) != 0)
info_format |= PNG_FORMAT_FLAG_ALPHA;
}
}
/* This is actually an internal error. */ if (info_format != format)
png_error(png_ptr, "png_read_image: invalid transformations");
}
/* Now read the rows. If do_local_compose is set then it is necessary to use * a local row buffer. The output will be GA, RGBA or BGRA and must be * converted to G, RGB or BGR as appropriate. The 'local_row' member of the * display acts as a flag.
*/
{
png_voidp first_row = display->buffer;
ptrdiff_t row_bytes = display->row_stride;
if (linear != 0)
row_bytes *= 2;
/* The following expression is designed to work correctly whether it gives * a signed or an unsigned result.
*/ if (row_bytes < 0)
{ char *ptr = png_voidcast(char*, first_row);
ptr += (image->height-1) * (-row_bytes);
first_row = png_voidcast(png_voidp, ptr);
}
while (--passes >= 0)
{
png_uint_32 y = image->height;
png_bytep row = png_voidcast(png_bytep, display->first_row);
for (; y > 0; --y)
{
png_read_row(png_ptr, row, NULL);
row += row_bytes;
}
}
return 1;
}
}
int PNGAPI
png_image_finish_read(png_imagep image, png_const_colorp background, void *buffer, png_int_32 row_stride, void *colormap)
{ if (image != NULL && image->version == PNG_IMAGE_VERSION)
{ /* Check for row_stride overflow. This check is not performed on the * original PNG format because it may not occur in the output PNG format * and libpng deals with the issues of reading the original.
*/ unsignedint channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
/* The following checks just the 'row_stride' calculation to ensure it * fits in a signed 32-bit value. Because channels/components can be * either 1 or 2 bytes in size the length of a row can still overflow 32 * bits; this is just to verify that the 'row_stride' argument can be * represented.
*/ if (image->width <= 0x7fffffffU/channels) /* no overflow */
{
png_uint_32 check;
png_uint_32 png_row_stride = image->width * channels;
if (row_stride == 0)
row_stride = (png_int_32)/*SAFE*/png_row_stride;
if (row_stride < 0)
check = (png_uint_32)(-row_stride);
else
check = (png_uint_32)row_stride;
/* This verifies 'check', the absolute value of the actual stride * passed in and detects overflow in the application calculation (i.e. * if the app did actually pass in a non-zero 'row_stride'.
*/ if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
{ /* Now check for overflow of the image buffer calculation; this * limits the whole image size to 32 bits for API compatibility with * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro. * * The PNG_IMAGE_BUFFER_SIZE macro is: * * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride)) * * And the component size is always 1 or 2, so make sure that the * number of *bytes* that the application is saying are available * does actually fit into a 32-bit number. * * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE * will be changed to use png_alloc_size_t; bigger images can be * accommodated on 64-bit systems.
*/ if (image->height <=
0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
{ if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
(image->colormap_entries > 0 && colormap != NULL))
{ int result;
png_image_read_control display;
/* Choose the correct 'end' routine; for the color-map case * all the setup has already been done.
*/ if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
result =
png_safe_execute(image,
png_image_read_colormap, &display) &&
png_safe_execute(image,
png_image_read_colormapped, &display);
else
result =
png_safe_execute(image,
png_image_read_direct, &display);
png_image_free(image); return result;
}
else return png_image_error(image, "png_image_finish_read[color-map]: no color-map");
}
else return png_image_error(image, "png_image_finish_read: image too large");
}
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