Impressum jdinput.c
Interaktion und PortierbarkeitC
/* * reserved comment block * DO NOT REMOVE OR ALTER!
*/ /* * jdinput.c * * Copyright (C) 1991-1997, Thomas G. Lane. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * * This file contains input control logic for the JPEG decompressor. * These routines are concerned with controlling the decompressor's input * processing (marker reading and coefficient decoding). The actual input * reading is done in jdmarker.c, jdhuff.c, and jdphuff.c.
*/
/* * Routines to calculate various quantities related to the size of the image.
*/
LOCAL(void)
initial_setup (j_decompress_ptr cinfo) /* Called once, when first SOS marker is reached */
{ int ci;
jpeg_component_info *compptr;
/* Make sure image isn't bigger than I can handle */ if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION ||
(long) cinfo->image_width > (long) JPEG_MAX_DIMENSION)
ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsignedint) JPEG_MAX_DIMENSION);
/* For now, precision must match compiled-in value... */ if (cinfo->data_precision != BITS_IN_JSAMPLE)
ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
/* Check that number of components won't exceed internal array sizes */ if (cinfo->num_components > MAX_COMPONENTS)
ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
MAX_COMPONENTS);
/* We initialize DCT_scaled_size and min_DCT_scaled_size to DCTSIZE. * In the full decompressor, this will be overridden by jdmaster.c; * but in the transcoder, jdmaster.c is not used, so we must do it here.
*/
cinfo->min_DCT_scaled_size = DCTSIZE;
/* Compute dimensions of components */ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
compptr->DCT_scaled_size = DCTSIZE; /* Size in DCT blocks */
compptr->width_in_blocks = (JDIMENSION)
jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
(long) (cinfo->max_h_samp_factor * DCTSIZE));
compptr->height_in_blocks = (JDIMENSION)
jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
(long) (cinfo->max_v_samp_factor * DCTSIZE)); /* downsampled_width and downsampled_height will also be overridden by * jdmaster.c if we are doing full decompression. The transcoder library * doesn't use these values, but the calling application might.
*/ /* Size in samples */
compptr->downsampled_width = (JDIMENSION)
jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
(long) cinfo->max_h_samp_factor);
compptr->downsampled_height = (JDIMENSION)
jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
(long) cinfo->max_v_samp_factor); /* Mark component needed, until color conversion says otherwise */
compptr->component_needed = TRUE; /* Mark no quantization table yet saved for component */
compptr->quant_table = NULL;
}
/* Compute number of fully interleaved MCU rows. */
cinfo->total_iMCU_rows = (JDIMENSION)
jdiv_round_up((long) cinfo->image_height,
(long) (cinfo->max_v_samp_factor*DCTSIZE));
LOCAL(void)
per_scan_setup (j_decompress_ptr cinfo) /* Do computations that are needed before processing a JPEG scan */ /* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */
{ int ci, mcublks, tmp;
jpeg_component_info *compptr;
/* For noninterleaved scan, always one block per MCU */
compptr->MCU_width = 1;
compptr->MCU_height = 1;
compptr->MCU_blocks = 1;
compptr->MCU_sample_width = compptr->DCT_scaled_size;
compptr->last_col_width = 1; /* For noninterleaved scans, it is convenient to define last_row_height * as the number of block rows present in the last iMCU row.
*/
tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor); if (tmp == 0) tmp = compptr->v_samp_factor;
compptr->last_row_height = tmp;
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci]; /* Sampling factors give # of blocks of component in each MCU */
compptr->MCU_width = compptr->h_samp_factor;
compptr->MCU_height = compptr->v_samp_factor;
compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_scaled_size; /* Figure number of non-dummy blocks in last MCU column & row */
tmp = (int) (compptr->width_in_blocks % compptr->MCU_width); if (tmp == 0) tmp = compptr->MCU_width;
compptr->last_col_width = tmp;
tmp = (int) (compptr->height_in_blocks % compptr->MCU_height); if (tmp == 0) tmp = compptr->MCU_height;
compptr->last_row_height = tmp; /* Prepare array describing MCU composition */
mcublks = compptr->MCU_blocks; if (cinfo->blocks_in_MCU + mcublks > D_MAX_BLOCKS_IN_MCU)
ERREXIT(cinfo, JERR_BAD_MCU_SIZE); while (mcublks-- > 0) {
cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
}
}
}
}
/* * Save away a copy of the Q-table referenced by each component present * in the current scan, unless already saved during a prior scan. * * In a multiple-scan JPEG file, the encoder could assign different components * the same Q-table slot number, but change table definitions between scans * so that each component uses a different Q-table. (The IJG encoder is not * currently capable of doing this, but other encoders might.) Since we want * to be able to dequantize all the components at the end of the file, this * means that we have to save away the table actually used for each component. * We do this by copying the table at the start of the first scan containing * the component. * The JPEG spec prohibits the encoder from changing the contents of a Q-table * slot between scans of a component using that slot. If the encoder does so * anyway, this decoder will simply use the Q-table values that were current * at the start of the first scan for the component. * * The decompressor output side looks only at the saved quant tables, * not at the current Q-table slots.
*/
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci]; /* No work if we already saved Q-table for this component */ if (compptr->quant_table != NULL) continue; /* Make sure specified quantization table is present */
qtblno = compptr->quant_tbl_no; if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
cinfo->quant_tbl_ptrs[qtblno] == NULL)
ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno); /* OK, save away the quantization table */
qtbl = (JQUANT_TBL *)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(JQUANT_TBL));
MEMCOPY(qtbl, cinfo->quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL));
compptr->quant_table = qtbl;
}
}
/* * Initialize the input modules to read a scan of compressed data. * The first call to this is done by jdmaster.c after initializing * the entire decompressor (during jpeg_start_decompress). * Subsequent calls come from consume_markers, below.
*/
/* * Finish up after inputting a compressed-data scan. * This is called by the coefficient controller after it's read all * the expected data of the scan.
*/
/* * Read JPEG markers before, between, or after compressed-data scans. * Change state as necessary when a new scan is reached. * Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI. * * The consume_input method pointer points either here or to the * coefficient controller's consume_data routine, depending on whether * we are reading a compressed data segment or inter-segment markers.
*/
if (inputctl->pub.eoi_reached) /* After hitting EOI, read no further */ return JPEG_REACHED_EOI;
val = (*cinfo->marker->read_markers) (cinfo);
switch (val) { case JPEG_REACHED_SOS: /* Found SOS */ if (inputctl->inheaders) { /* 1st SOS */
initial_setup(cinfo);
inputctl->inheaders = FALSE; /* Note: start_input_pass must be called by jdmaster.c * before any more input can be consumed. jdapimin.c is * responsible for enforcing this sequencing.
*/
} else { /* 2nd or later SOS marker */ if (! inputctl->pub.has_multiple_scans)
ERREXIT(cinfo, JERR_EOI_EXPECTED); /* Oops, I wasn't expecting this! */
start_input_pass(cinfo);
} break; case JPEG_REACHED_EOI: /* Found EOI */
inputctl->pub.eoi_reached = TRUE; if (inputctl->inheaders) { /* Tables-only datastream, apparently */ if (cinfo->marker->saw_SOF)
ERREXIT(cinfo, JERR_SOF_NO_SOS);
} else { /* Prevent infinite loop in coef ctlr's decompress_data routine * if user set output_scan_number larger than number of scans.
*/ if (cinfo->output_scan_number > cinfo->input_scan_number)
cinfo->output_scan_number = cinfo->input_scan_number;
} break; case JPEG_SUSPENDED: break;
}
/* Create subobject in permanent pool */
inputctl = (my_inputctl_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(my_input_controller));
cinfo->inputctl = (struct jpeg_input_controller *) inputctl; /* Initialize method pointers */
inputctl->pub.consume_input = consume_markers;
inputctl->pub.reset_input_controller = reset_input_controller;
inputctl->pub.start_input_pass = start_input_pass;
inputctl->pub.finish_input_pass = finish_input_pass; /* Initialize state: can't use reset_input_controller since we don't * want to try to reset other modules yet.
*/
inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
inputctl->pub.eoi_reached = FALSE;
inputctl->inheaders = TRUE;
}
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