429 lines
16 KiB
C++
429 lines
16 KiB
C++
// * jccoefct.c
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// *
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// * Copyright (C) 1994-1995, Thomas G. Lane.
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// * This file is part of the Independent JPEG Group's software.
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// * For conditions of distribution and use, see the accompanying README file.
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// *
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// * This file contains the coefficient buffer controller for compression.
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// * This controller is the top level of the JPEG compressor proper.
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// * The coefficient buffer lies between forward-DCT and entropy encoding steps.
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#define JPEG_INTERNALS
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#include "JINCLUDE.h"
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#include "JPEGLIB.h"
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// We use a full-image coefficient buffer when doing Huffman optimization,
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// * and also for writing multiple-scan JPEG files. In all cases, the DCT
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// * step is run during the first pass, and subsequent passes need only read
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// * the buffered coefficients.
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#ifdef ENTROPY_OPT_SUPPORTED
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#define FULL_COEF_BUFFER_SUPPORTED
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#else
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#ifdef C_MULTISCAN_FILES_SUPPORTED
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#define FULL_COEF_BUFFER_SUPPORTED
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#endif
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#endif
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// Private buffer controller object
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typedef struct {
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struct jpeg_c_coef_controller pub; // public fields
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JDIMENSION iMCU_row_num; // iMCU row # within image
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JDIMENSION mcu_ctr; // counts MCUs processed in current row
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int MCU_vert_offset; // counts MCU rows within iMCU row
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int MCU_rows_per_iMCU_row; // number of such rows needed
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// For single-pass compression, it's sufficient to buffer just one MCU
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// * (although this may prove a bit slow in practice). We allocate a
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// * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
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// * MCU constructed and sent. (On 80x86, the workspace is FAR even though
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// * it's not really very big; this is to keep the module interfaces unchanged
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// * when a large coefficient buffer is necessary.)
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// * In multi-pass modes, this array points to the current MCU's blocks
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// * within the virtual arrays.
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JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
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// In multi-pass modes, we need a virtual block array for each component.
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jvirt_barray_ptr whole_image[MAX_COMPONENTS];
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} my_coef_controller;
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typedef my_coef_controller * my_coef_ptr;
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// Forward declarations
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METHODDEF boolean compress_data
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JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
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#ifdef FULL_COEF_BUFFER_SUPPORTED
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METHODDEF boolean compress_first_pass
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JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
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METHODDEF boolean compress_output
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JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
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#endif
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LOCAL void
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start_iMCU_row (j_compress_ptr cinfo)
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// Reset within-iMCU-row counters for a new row
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{
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my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
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// In an interleaved scan, an MCU row is the same as an iMCU row.
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// * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
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// * But at the bottom of the image, process only what's left.
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if (cinfo->comps_in_scan > 1) {
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coef->MCU_rows_per_iMCU_row = 1;
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} else {
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if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
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coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
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else
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coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
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}
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coef->mcu_ctr = 0;
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coef->MCU_vert_offset = 0;
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}
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// * Initialize for a processing pass.
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METHODDEF void
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start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
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{
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my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
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coef->iMCU_row_num = 0;
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start_iMCU_row(cinfo);
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switch (pass_mode) {
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case JBUF_PASS_THRU:
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if (coef->whole_image[0] != NULL)
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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coef->pub.compress_data = compress_data;
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break;
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#ifdef FULL_COEF_BUFFER_SUPPORTED
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case JBUF_SAVE_AND_PASS:
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if (coef->whole_image[0] == NULL)
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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coef->pub.compress_data = compress_first_pass;
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break;
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case JBUF_CRANK_DEST:
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if (coef->whole_image[0] == NULL)
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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coef->pub.compress_data = compress_output;
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break;
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#endif
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default:
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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break;
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}
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}
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// * Process some data in the single-pass case.
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// * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
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// * per call, ie, v_samp_factor block rows for each component in the image.
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// * Returns TRUE if the iMCU row is completed, FALSE if suspended.
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// *
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// * NB: input_buf contains a plane for each component in image.
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// * For single pass, this is the same as the components in the scan.
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METHODDEF boolean
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compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
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{
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my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
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JDIMENSION MCU_col_num; // index of current MCU within row
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JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
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JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
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int blkn, bi, ci, yindex, yoffset, blockcnt;
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JDIMENSION ypos, xpos;
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jpeg_component_info *compptr;
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// Loop to write as much as one whole iMCU row
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for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
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yoffset++) {
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for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
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MCU_col_num++) {
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// Determine where data comes from in input_buf and do the DCT thing.
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// * Each call on forward_DCT processes a horizontal row of DCT blocks
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// * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
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// * sequentially. Dummy blocks at the right or bottom edge are filled in
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// * specially. The data in them does not matter for image reconstruction,
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// * so we fill them with values that will encode to the smallest amount of
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// * data, viz: all zeroes in the AC entries, DC entries equal to previous
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// * block's DC value. (Thanks to Thomas Kinsman for this idea.)
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blkn = 0;
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for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
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compptr = cinfo->cur_comp_info[ci];
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blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
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: compptr->last_col_width;
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xpos = MCU_col_num * compptr->MCU_sample_width;
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ypos = yoffset * DCTSIZE; // ypos == (yoffset+yindex) * DCTSIZE
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for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
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if (coef->iMCU_row_num < last_iMCU_row ||
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yoffset+yindex < compptr->last_row_height) {
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(*cinfo->fdct->forward_DCT) (cinfo, compptr,
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input_buf[ci], coef->MCU_buffer[blkn],
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ypos, xpos, (JDIMENSION) blockcnt);
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if (blockcnt < compptr->MCU_width) {
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// Create some dummy blocks at the right edge of the image.
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jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
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(compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
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for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
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coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
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}
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}
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} else {
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// Create a row of dummy blocks at the bottom of the image.
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jzero_far((void FAR *) coef->MCU_buffer[blkn],
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compptr->MCU_width * SIZEOF(JBLOCK));
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for (bi = 0; bi < compptr->MCU_width; bi++) {
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coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
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}
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}
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blkn += compptr->MCU_width;
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ypos += DCTSIZE;
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}
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}
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// Try to write the MCU. In event of a suspension failure, we will
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// * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
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if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
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// Suspension forced; update state counters and exit
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coef->MCU_vert_offset = yoffset;
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coef->mcu_ctr = MCU_col_num;
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return FALSE;
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}
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}
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// Completed an MCU row, but perhaps not an iMCU row
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coef->mcu_ctr = 0;
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}
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// Completed the iMCU row, advance counters for next one
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coef->iMCU_row_num++;
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start_iMCU_row(cinfo);
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return TRUE;
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}
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#ifdef FULL_COEF_BUFFER_SUPPORTED
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// * Process some data in the first pass of a multi-pass case.
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// * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
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// * per call, ie, v_samp_factor block rows for each component in the image.
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// * This amount of data is read from the source buffer, DCT'd and quantized,
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// * and saved into the virtual arrays. We also generate suitable dummy blocks
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// * as needed at the right and lower edges. (The dummy blocks are constructed
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// * in the virtual arrays, which have been padded appropriately.) This makes
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// * it possible for subsequent passes not to worry about real vs. dummy blocks.
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// *
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// * We must also emit the data to the entropy encoder. This is conveniently
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// * done by calling compress_output() after we've loaded the current strip
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// * of the virtual arrays.
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// *
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// * NB: input_buf contains a plane for each component in image. All
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// * components are DCT'd and loaded into the virtual arrays in this pass.
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// * However, it may be that only a subset of the components are emitted to
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// * the entropy encoder during this first pass; be careful about looking
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// * at the scan-dependent variables (MCU dimensions, etc).
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METHODDEF boolean
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compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
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{
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my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
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JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
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JDIMENSION blocks_across, MCUs_across, MCUindex;
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int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
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JCOEF lastDC;
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jpeg_component_info *compptr;
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JBLOCKARRAY buffer;
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JBLOCKROW thisblockrow, lastblockrow;
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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// Align the virtual buffer for this component.
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buffer = (*cinfo->mem->access_virt_barray)
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((j_common_ptr) cinfo, coef->whole_image[ci],
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coef->iMCU_row_num * compptr->v_samp_factor,
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(JDIMENSION) compptr->v_samp_factor, TRUE);
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// Count non-dummy DCT block rows in this iMCU row.
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if (coef->iMCU_row_num < last_iMCU_row)
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block_rows = compptr->v_samp_factor;
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else {
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// NB: can't use last_row_height here, since may not be set!
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block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
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if (block_rows == 0) block_rows = compptr->v_samp_factor;
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}
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blocks_across = compptr->width_in_blocks;
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h_samp_factor = compptr->h_samp_factor;
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// Count number of dummy blocks to be added at the right margin.
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ndummy = (int) (blocks_across % h_samp_factor);
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if (ndummy > 0)
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ndummy = h_samp_factor - ndummy;
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// Perform DCT for all non-dummy blocks in this iMCU row. Each call
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// * on forward_DCT processes a complete horizontal row of DCT blocks.
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for (block_row = 0; block_row < block_rows; block_row++) {
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thisblockrow = buffer[block_row];
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(*cinfo->fdct->forward_DCT) (cinfo, compptr,
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input_buf[ci], thisblockrow,
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(JDIMENSION) (block_row * DCTSIZE),
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(JDIMENSION) 0, blocks_across);
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if (ndummy > 0) {
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// Create dummy blocks at the right edge of the image.
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thisblockrow += blocks_across; // => first dummy block
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jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
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lastDC = thisblockrow[-1][0];
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for (bi = 0; bi < ndummy; bi++) {
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thisblockrow[bi][0] = lastDC;
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}
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}
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}
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// If at end of image, create dummy block rows as needed.
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// * The tricky part here is that within each MCU, we want the DC values
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// * of the dummy blocks to match the last real block's DC value.
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// * This squeezes a few more bytes out of the resulting file...
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if (coef->iMCU_row_num == last_iMCU_row) {
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blocks_across += ndummy; // include lower right corner
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MCUs_across = blocks_across / h_samp_factor;
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for (block_row = block_rows; block_row < compptr->v_samp_factor;
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block_row++) {
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thisblockrow = buffer[block_row];
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lastblockrow = buffer[block_row-1];
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jzero_far((void FAR *) thisblockrow,
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(size_t) (blocks_across * SIZEOF(JBLOCK)));
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for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
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lastDC = lastblockrow[h_samp_factor-1][0];
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for (bi = 0; bi < h_samp_factor; bi++) {
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thisblockrow[bi][0] = lastDC;
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}
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thisblockrow += h_samp_factor; // advance to next MCU in row
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lastblockrow += h_samp_factor;
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}
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}
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}
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}
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// NB: compress_output will increment iMCU_row_num if successful.
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// * A suspension return will result in redoing all the work above next time.
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// Emit data to the entropy encoder, sharing code with subsequent passes
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return compress_output(cinfo, input_buf);
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}
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// * Process some data in subsequent passes of a multi-pass case.
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// * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
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// * per call, ie, v_samp_factor block rows for each component in the scan.
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// * The data is obtained from the virtual arrays and fed to the entropy coder.
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// * Returns TRUE if the iMCU row is completed, FALSE if suspended.
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// *
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// * NB: input_buf is ignored; it is likely to be a NULL pointer.
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METHODDEF boolean
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compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
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{
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my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
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JDIMENSION MCU_col_num; // index of current MCU within row
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int blkn, ci, xindex, yindex, yoffset;
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JDIMENSION start_col;
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JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
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JBLOCKROW buffer_ptr;
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jpeg_component_info *compptr;
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// Align the virtual buffers for the components used in this scan.
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// * NB: during first pass, this is safe only because the buffers will
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// * already be aligned properly, so jmemmgr.c won't need to do any I/O.
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for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
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compptr = cinfo->cur_comp_info[ci];
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buffer[ci] = (*cinfo->mem->access_virt_barray)
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((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
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coef->iMCU_row_num * compptr->v_samp_factor,
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(JDIMENSION) compptr->v_samp_factor, FALSE);
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}
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// Loop to process one whole iMCU row
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for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
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yoffset++) {
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for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
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MCU_col_num++) {
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// Construct list of pointers to DCT blocks belonging to this MCU
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blkn = 0; // index of current DCT block within MCU
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for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
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compptr = cinfo->cur_comp_info[ci];
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start_col = MCU_col_num * compptr->MCU_width;
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for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
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buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
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for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
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coef->MCU_buffer[blkn++] = buffer_ptr++;
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}
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}
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}
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// Try to write the MCU.
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if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
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// Suspension forced; update state counters and exit
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coef->MCU_vert_offset = yoffset;
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coef->mcu_ctr = MCU_col_num;
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return FALSE;
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}
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}
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// Completed an MCU row, but perhaps not an iMCU row
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coef->mcu_ctr = 0;
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}
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// Completed the iMCU row, advance counters for next one
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coef->iMCU_row_num++;
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start_iMCU_row(cinfo);
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return TRUE;
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}
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#endif // FULL_COEF_BUFFER_SUPPORTED
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// * Initialize coefficient buffer controller.
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GLOBAL void
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jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
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{
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my_coef_ptr coef;
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coef = (my_coef_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(my_coef_controller));
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cinfo->coef = (struct jpeg_c_coef_controller *) coef;
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coef->pub.start_pass = start_pass_coef;
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// Create the coefficient buffer.
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if (need_full_buffer) {
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#ifdef FULL_COEF_BUFFER_SUPPORTED
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// Allocate a full-image virtual array for each component,
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// padded to a multiple of samp_factor DCT blocks in each direction.
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int ci;
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jpeg_component_info *compptr;
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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ci++, compptr++) {
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coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
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((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
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(JDIMENSION) jround_up((LONG) compptr->width_in_blocks,
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(LONG) compptr->h_samp_factor),
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(JDIMENSION) jround_up((LONG) compptr->height_in_blocks,
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(LONG) compptr->v_samp_factor),
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(JDIMENSION) compptr->v_samp_factor);
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}
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#else
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ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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#endif
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} else {
|
|
// We only need a single-MCU buffer.
|
|
JBLOCKROW buffer;
|
|
int i;
|
|
|
|
buffer = (JBLOCKROW)
|
|
(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
|
|
C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
|
|
for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
|
|
coef->MCU_buffer[i] = buffer + i;
|
|
}
|
|
coef->whole_image[0] = NULL; // flag for no virtual arrays
|
|
}
|
|
}
|