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