/* 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);
for (a=1; a<5; ++a)
{ unsignedint g;
for (g=0; g<6; ++g)
--> --------------------
--> maximum size reached
--> --------------------
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