0N/A/*
0N/A * reserved comment block
0N/A * DO NOT REMOVE OR ALTER!
0N/A */
0N/A/*
0N/A * jdmainct.c
0N/A *
0N/A * Copyright (C) 1994-1996, Thomas G. Lane.
0N/A * This file is part of the Independent JPEG Group's software.
0N/A * For conditions of distribution and use, see the accompanying README file.
0N/A *
0N/A * This file contains the main buffer controller for decompression.
0N/A * The main buffer lies between the JPEG decompressor proper and the
0N/A * post-processor; it holds downsampled data in the JPEG colorspace.
0N/A *
0N/A * Note that this code is bypassed in raw-data mode, since the application
0N/A * supplies the equivalent of the main buffer in that case.
0N/A */
0N/A
0N/A#define JPEG_INTERNALS
0N/A#include "jinclude.h"
0N/A#include "jpeglib.h"
0N/A
0N/A
0N/A/*
0N/A * In the current system design, the main buffer need never be a full-image
0N/A * buffer; any full-height buffers will be found inside the coefficient or
0N/A * postprocessing controllers. Nonetheless, the main controller is not
0N/A * trivial. Its responsibility is to provide context rows for upsampling/
0N/A * rescaling, and doing this in an efficient fashion is a bit tricky.
0N/A *
0N/A * Postprocessor input data is counted in "row groups". A row group
0N/A * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
0N/A * sample rows of each component. (We require DCT_scaled_size values to be
0N/A * chosen such that these numbers are integers. In practice DCT_scaled_size
0N/A * values will likely be powers of two, so we actually have the stronger
0N/A * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
0N/A * Upsampling will typically produce max_v_samp_factor pixel rows from each
0N/A * row group (times any additional scale factor that the upsampler is
0N/A * applying).
0N/A *
0N/A * The coefficient controller will deliver data to us one iMCU row at a time;
0N/A * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
0N/A * exactly min_DCT_scaled_size row groups. (This amount of data corresponds
0N/A * to one row of MCUs when the image is fully interleaved.) Note that the
0N/A * number of sample rows varies across components, but the number of row
0N/A * groups does not. Some garbage sample rows may be included in the last iMCU
0N/A * row at the bottom of the image.
0N/A *
0N/A * Depending on the vertical scaling algorithm used, the upsampler may need
0N/A * access to the sample row(s) above and below its current input row group.
0N/A * The upsampler is required to set need_context_rows TRUE at global selection
0N/A * time if so. When need_context_rows is FALSE, this controller can simply
0N/A * obtain one iMCU row at a time from the coefficient controller and dole it
0N/A * out as row groups to the postprocessor.
0N/A *
0N/A * When need_context_rows is TRUE, this controller guarantees that the buffer
0N/A * passed to postprocessing contains at least one row group's worth of samples
0N/A * above and below the row group(s) being processed. Note that the context
0N/A * rows "above" the first passed row group appear at negative row offsets in
0N/A * the passed buffer. At the top and bottom of the image, the required
0N/A * context rows are manufactured by duplicating the first or last real sample
0N/A * row; this avoids having special cases in the upsampling inner loops.
0N/A *
0N/A * The amount of context is fixed at one row group just because that's a
0N/A * convenient number for this controller to work with. The existing
0N/A * upsamplers really only need one sample row of context. An upsampler
0N/A * supporting arbitrary output rescaling might wish for more than one row
0N/A * group of context when shrinking the image; tough, we don't handle that.
0N/A * (This is justified by the assumption that downsizing will be handled mostly
0N/A * by adjusting the DCT_scaled_size values, so that the actual scale factor at
0N/A * the upsample step needn't be much less than one.)
0N/A *
0N/A * To provide the desired context, we have to retain the last two row groups
0N/A * of one iMCU row while reading in the next iMCU row. (The last row group
0N/A * can't be processed until we have another row group for its below-context,
0N/A * and so we have to save the next-to-last group too for its above-context.)
0N/A * We could do this most simply by copying data around in our buffer, but
0N/A * that'd be very slow. We can avoid copying any data by creating a rather
0N/A * strange pointer structure. Here's how it works. We allocate a workspace
0N/A * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
0N/A * of row groups per iMCU row). We create two sets of redundant pointers to
0N/A * the workspace. Labeling the physical row groups 0 to M+1, the synthesized
0N/A * pointer lists look like this:
0N/A * M+1 M-1
0N/A * master pointer --> 0 master pointer --> 0
0N/A * 1 1
0N/A * ... ...
0N/A * M-3 M-3
0N/A * M-2 M
0N/A * M-1 M+1
0N/A * M M-2
0N/A * M+1 M-1
0N/A * 0 0
0N/A * We read alternate iMCU rows using each master pointer; thus the last two
0N/A * row groups of the previous iMCU row remain un-overwritten in the workspace.
0N/A * The pointer lists are set up so that the required context rows appear to
0N/A * be adjacent to the proper places when we pass the pointer lists to the
0N/A * upsampler.
0N/A *
0N/A * The above pictures describe the normal state of the pointer lists.
0N/A * At top and bottom of the image, we diddle the pointer lists to duplicate
0N/A * the first or last sample row as necessary (this is cheaper than copying
0N/A * sample rows around).
0N/A *
0N/A * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1. In that
0N/A * situation each iMCU row provides only one row group so the buffering logic
0N/A * must be different (eg, we must read two iMCU rows before we can emit the
0N/A * first row group). For now, we simply do not support providing context
0N/A * rows when min_DCT_scaled_size is 1. That combination seems unlikely to
0N/A * be worth providing --- if someone wants a 1/8th-size preview, they probably
0N/A * want it quick and dirty, so a context-free upsampler is sufficient.
0N/A */
0N/A
0N/A
0N/A/* Private buffer controller object */
0N/A
0N/Atypedef struct {
0N/A struct jpeg_d_main_controller pub; /* public fields */
0N/A
0N/A /* Pointer to allocated workspace (M or M+2 row groups). */
0N/A JSAMPARRAY buffer[MAX_COMPONENTS];
0N/A
0N/A boolean buffer_full; /* Have we gotten an iMCU row from decoder? */
0N/A JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */
0N/A
0N/A /* Remaining fields are only used in the context case. */
0N/A
0N/A /* These are the master pointers to the funny-order pointer lists. */
0N/A JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */
0N/A
0N/A int whichptr; /* indicates which pointer set is now in use */
0N/A int context_state; /* process_data state machine status */
0N/A JDIMENSION rowgroups_avail; /* row groups available to postprocessor */
0N/A JDIMENSION iMCU_row_ctr; /* counts iMCU rows to detect image top/bot */
0N/A} my_main_controller;
0N/A
0N/Atypedef my_main_controller * my_main_ptr;
0N/A
0N/A/* context_state values: */
0N/A#define CTX_PREPARE_FOR_IMCU 0 /* need to prepare for MCU row */
0N/A#define CTX_PROCESS_IMCU 1 /* feeding iMCU to postprocessor */
0N/A#define CTX_POSTPONED_ROW 2 /* feeding postponed row group */
0N/A
0N/A
0N/A/* Forward declarations */
0N/AMETHODDEF(void) process_data_simple_main
0N/A JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
0N/A JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
0N/AMETHODDEF(void) process_data_context_main
0N/A JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
0N/A JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
0N/A#ifdef QUANT_2PASS_SUPPORTED
0N/AMETHODDEF(void) process_data_crank_post
0N/A JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
0N/A JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
0N/A#endif
0N/A
0N/A
0N/ALOCAL(void)
0N/Aalloc_funny_pointers (j_decompress_ptr cinfo)
0N/A/* Allocate space for the funny pointer lists.
0N/A * This is done only once, not once per pass.
0N/A */
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A int ci, rgroup;
0N/A int M = cinfo->min_DCT_scaled_size;
0N/A jpeg_component_info *compptr;
0N/A JSAMPARRAY xbuf;
0N/A
0N/A /* Get top-level space for component array pointers.
0N/A * We alloc both arrays with one call to save a few cycles.
0N/A */
0N/A _main->xbuffer[0] = (JSAMPIMAGE)
0N/A (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
0N/A cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
0N/A _main->xbuffer[1] = _main->xbuffer[0] + cinfo->num_components;
0N/A
0N/A for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
0N/A ci++, compptr++) {
0N/A rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
0N/A cinfo->min_DCT_scaled_size; /* height of a row group of component */
0N/A /* Get space for pointer lists --- M+4 row groups in each list.
0N/A * We alloc both pointer lists with one call to save a few cycles.
0N/A */
0N/A xbuf = (JSAMPARRAY)
0N/A (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
0N/A 2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
0N/A xbuf += rgroup; /* want one row group at negative offsets */
0N/A _main->xbuffer[0][ci] = xbuf;
0N/A xbuf += rgroup * (M + 4);
0N/A _main->xbuffer[1][ci] = xbuf;
0N/A }
0N/A}
0N/A
0N/A
0N/ALOCAL(void)
0N/Amake_funny_pointers (j_decompress_ptr cinfo)
0N/A/* Create the funny pointer lists discussed in the comments above.
0N/A * The actual workspace is already allocated (in main->buffer),
0N/A * and the space for the pointer lists is allocated too.
0N/A * This routine just fills in the curiously ordered lists.
0N/A * This will be repeated at the beginning of each pass.
0N/A */
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A int ci, i, rgroup;
0N/A int M = cinfo->min_DCT_scaled_size;
0N/A jpeg_component_info *compptr;
0N/A JSAMPARRAY buf, xbuf0, xbuf1;
0N/A
0N/A for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
0N/A ci++, compptr++) {
0N/A rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
0N/A cinfo->min_DCT_scaled_size; /* height of a row group of component */
0N/A xbuf0 = _main->xbuffer[0][ci];
0N/A xbuf1 = _main->xbuffer[1][ci];
0N/A /* First copy the workspace pointers as-is */
0N/A buf = _main->buffer[ci];
0N/A for (i = 0; i < rgroup * (M + 2); i++) {
0N/A xbuf0[i] = xbuf1[i] = buf[i];
0N/A }
0N/A /* In the second list, put the last four row groups in swapped order */
0N/A for (i = 0; i < rgroup * 2; i++) {
0N/A xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
0N/A xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
0N/A }
0N/A /* The wraparound pointers at top and bottom will be filled later
0N/A * (see set_wraparound_pointers, below). Initially we want the "above"
0N/A * pointers to duplicate the first actual data line. This only needs
0N/A * to happen in xbuffer[0].
0N/A */
0N/A for (i = 0; i < rgroup; i++) {
0N/A xbuf0[i - rgroup] = xbuf0[0];
0N/A }
0N/A }
0N/A}
0N/A
0N/A
0N/ALOCAL(void)
0N/Aset_wraparound_pointers (j_decompress_ptr cinfo)
0N/A/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
0N/A * This changes the pointer list state from top-of-image to the normal state.
0N/A */
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A int ci, i, rgroup;
0N/A int M = cinfo->min_DCT_scaled_size;
0N/A jpeg_component_info *compptr;
0N/A JSAMPARRAY xbuf0, xbuf1;
0N/A
0N/A for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
0N/A ci++, compptr++) {
0N/A rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
0N/A cinfo->min_DCT_scaled_size; /* height of a row group of component */
0N/A xbuf0 = _main->xbuffer[0][ci];
0N/A xbuf1 = _main->xbuffer[1][ci];
0N/A for (i = 0; i < rgroup; i++) {
0N/A xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
0N/A xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
0N/A xbuf0[rgroup*(M+2) + i] = xbuf0[i];
0N/A xbuf1[rgroup*(M+2) + i] = xbuf1[i];
0N/A }
0N/A }
0N/A}
0N/A
0N/A
0N/ALOCAL(void)
0N/Aset_bottom_pointers (j_decompress_ptr cinfo)
0N/A/* Change the pointer lists to duplicate the last sample row at the bottom
0N/A * of the image. whichptr indicates which xbuffer holds the final iMCU row.
0N/A * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
0N/A */
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A int ci, i, rgroup, iMCUheight, rows_left;
0N/A jpeg_component_info *compptr;
0N/A JSAMPARRAY xbuf;
0N/A
0N/A for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
0N/A ci++, compptr++) {
0N/A /* Count sample rows in one iMCU row and in one row group */
0N/A iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
0N/A rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
0N/A /* Count nondummy sample rows remaining for this component */
0N/A rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
0N/A if (rows_left == 0) rows_left = iMCUheight;
0N/A /* Count nondummy row groups. Should get same answer for each component,
0N/A * so we need only do it once.
0N/A */
0N/A if (ci == 0) {
0N/A _main->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
0N/A }
0N/A /* Duplicate the last real sample row rgroup*2 times; this pads out the
0N/A * last partial rowgroup and ensures at least one full rowgroup of context.
0N/A */
0N/A xbuf = _main->xbuffer[_main->whichptr][ci];
0N/A for (i = 0; i < rgroup * 2; i++) {
0N/A xbuf[rows_left + i] = xbuf[rows_left-1];
0N/A }
0N/A }
0N/A}
0N/A
0N/A
0N/A/*
0N/A * Initialize for a processing pass.
0N/A */
0N/A
0N/AMETHODDEF(void)
0N/Astart_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A
0N/A switch (pass_mode) {
0N/A case JBUF_PASS_THRU:
0N/A if (cinfo->upsample->need_context_rows) {
0N/A _main->pub.process_data = process_data_context_main;
0N/A make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
0N/A _main->whichptr = 0; /* Read first iMCU row into xbuffer[0] */
0N/A _main->context_state = CTX_PREPARE_FOR_IMCU;
0N/A _main->iMCU_row_ctr = 0;
0N/A } else {
0N/A /* Simple case with no context needed */
0N/A _main->pub.process_data = process_data_simple_main;
0N/A }
0N/A _main->buffer_full = FALSE; /* Mark buffer empty */
0N/A _main->rowgroup_ctr = 0;
0N/A break;
0N/A#ifdef QUANT_2PASS_SUPPORTED
0N/A case JBUF_CRANK_DEST:
0N/A /* For last pass of 2-pass quantization, just crank the postprocessor */
0N/A _main->pub.process_data = process_data_crank_post;
0N/A break;
0N/A#endif
0N/A default:
0N/A ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
0N/A break;
0N/A }
0N/A}
0N/A
0N/A
0N/A/*
0N/A * Process some data.
0N/A * This handles the simple case where no context is required.
0N/A */
0N/A
0N/AMETHODDEF(void)
0N/Aprocess_data_simple_main (j_decompress_ptr cinfo,
0N/A JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
0N/A JDIMENSION out_rows_avail)
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A JDIMENSION rowgroups_avail;
0N/A
0N/A /* Read input data if we haven't filled the main buffer yet */
0N/A if (! _main->buffer_full) {
0N/A if (! (*cinfo->coef->decompress_data) (cinfo, _main->buffer))
0N/A return; /* suspension forced, can do nothing more */
0N/A _main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
0N/A }
0N/A
0N/A /* There are always min_DCT_scaled_size row groups in an iMCU row. */
0N/A rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size;
0N/A /* Note: at the bottom of the image, we may pass extra garbage row groups
0N/A * to the postprocessor. The postprocessor has to check for bottom
0N/A * of image anyway (at row resolution), so no point in us doing it too.
0N/A */
0N/A
0N/A /* Feed the postprocessor */
0N/A (*cinfo->post->post_process_data) (cinfo, _main->buffer,
0N/A &_main->rowgroup_ctr, rowgroups_avail,
0N/A output_buf, out_row_ctr, out_rows_avail);
0N/A
0N/A /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
0N/A if (_main->rowgroup_ctr >= rowgroups_avail) {
0N/A _main->buffer_full = FALSE;
0N/A _main->rowgroup_ctr = 0;
0N/A }
0N/A}
0N/A
0N/A
0N/A/*
0N/A * Process some data.
0N/A * This handles the case where context rows must be provided.
0N/A */
0N/A
0N/AMETHODDEF(void)
0N/Aprocess_data_context_main (j_decompress_ptr cinfo,
0N/A JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
0N/A JDIMENSION out_rows_avail)
0N/A{
0N/A my_main_ptr _main = (my_main_ptr) cinfo->main;
0N/A
0N/A /* Read input data if we haven't filled the _main buffer yet */
0N/A if (! _main->buffer_full) {
0N/A if (! (*cinfo->coef->decompress_data) (cinfo,
0N/A _main->xbuffer[_main->whichptr]))
0N/A return; /* suspension forced, can do nothing more */
0N/A _main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
0N/A _main->iMCU_row_ctr++; /* count rows received */
0N/A }
0N/A
0N/A /* Postprocessor typically will not swallow all the input data it is handed
0N/A * in one call (due to filling the output buffer first). Must be prepared
0N/A * to exit and restart. This switch lets us keep track of how far we got.
0N/A * Note that each case falls through to the next on successful completion.
0N/A */
0N/A switch (_main->context_state) {
0N/A case CTX_POSTPONED_ROW:
0N/A /* Call postprocessor using previously set pointers for postponed row */
0N/A (*cinfo->post->post_process_data) (cinfo, _main->xbuffer[_main->whichptr],
0N/A &_main->rowgroup_ctr, _main->rowgroups_avail,
0N/A output_buf, out_row_ctr, out_rows_avail);
0N/A if (_main->rowgroup_ctr < _main->rowgroups_avail)
0N/A return; /* Need to suspend */
0N/A _main->context_state = CTX_PREPARE_FOR_IMCU;
0N/A if (*out_row_ctr >= out_rows_avail)
0N/A return; /* Postprocessor exactly filled output buf */
0N/A /*FALLTHROUGH*/
0N/A case CTX_PREPARE_FOR_IMCU:
0N/A /* Prepare to process first M-1 row groups of this iMCU row */
0N/A _main->rowgroup_ctr = 0;
0N/A _main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1);
0N/A /* Check for bottom of image: if so, tweak pointers to "duplicate"
0N/A * the last sample row, and adjust rowgroups_avail to ignore padding rows.
0N/A */
0N/A if (_main->iMCU_row_ctr == cinfo->total_iMCU_rows)
0N/A set_bottom_pointers(cinfo);
0N/A _main->context_state = CTX_PROCESS_IMCU;
0N/A /*FALLTHROUGH*/
0N/A case CTX_PROCESS_IMCU:
0N/A /* Call postprocessor using previously set pointers */
0N/A (*cinfo->post->post_process_data) (cinfo, _main->xbuffer[_main->whichptr],
0N/A &_main->rowgroup_ctr, _main->rowgroups_avail,
0N/A output_buf, out_row_ctr, out_rows_avail);
0N/A if (_main->rowgroup_ctr < _main->rowgroups_avail)
0N/A return; /* Need to suspend */
0N/A /* After the first iMCU, change wraparound pointers to normal state */
0N/A if (_main->iMCU_row_ctr == 1)
0N/A set_wraparound_pointers(cinfo);
0N/A /* Prepare to load new iMCU row using other xbuffer list */
0N/A _main->whichptr ^= 1; /* 0=>1 or 1=>0 */
0N/A _main->buffer_full = FALSE;
0N/A /* Still need to process last row group of this iMCU row, */
0N/A /* which is saved at index M+1 of the other xbuffer */
0N/A _main->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1);
0N/A _main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2);
0N/A _main->context_state = CTX_POSTPONED_ROW;
0N/A }
0N/A}
0N/A
0N/A
0N/A/*
0N/A * Process some data.
0N/A * Final pass of two-pass quantization: just call the postprocessor.
0N/A * Source data will be the postprocessor controller's internal buffer.
0N/A */
0N/A
0N/A#ifdef QUANT_2PASS_SUPPORTED
0N/A
0N/AMETHODDEF(void)
0N/Aprocess_data_crank_post (j_decompress_ptr cinfo,
0N/A JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
0N/A JDIMENSION out_rows_avail)
0N/A{
0N/A (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
0N/A (JDIMENSION *) NULL, (JDIMENSION) 0,
0N/A output_buf, out_row_ctr, out_rows_avail);
0N/A}
0N/A
0N/A#endif /* QUANT_2PASS_SUPPORTED */
0N/A
0N/A
0N/A/*
0N/A * Initialize main buffer controller.
0N/A */
0N/A
0N/AGLOBAL(void)
0N/Ajinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
0N/A{
0N/A my_main_ptr _main;
0N/A int ci, rgroup, ngroups;
0N/A jpeg_component_info *compptr;
0N/A
0N/A _main = (my_main_ptr)
0N/A (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
0N/A SIZEOF(my_main_controller));
0N/A cinfo->main = (struct jpeg_d_main_controller *) _main;
0N/A _main->pub.start_pass = start_pass_main;
0N/A
0N/A if (need_full_buffer) /* shouldn't happen */
0N/A ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
0N/A
0N/A /* Allocate the workspace.
0N/A * ngroups is the number of row groups we need.
0N/A */
0N/A if (cinfo->upsample->need_context_rows) {
0N/A if (cinfo->min_DCT_scaled_size < 2) /* unsupported, see comments above */
0N/A ERREXIT(cinfo, JERR_NOTIMPL);
0N/A alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
0N/A ngroups = cinfo->min_DCT_scaled_size + 2;
0N/A } else {
0N/A ngroups = cinfo->min_DCT_scaled_size;
0N/A }
0N/A
0N/A for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
0N/A ci++, compptr++) {
0N/A rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
0N/A cinfo->min_DCT_scaled_size; /* height of a row group of component */
0N/A _main->buffer[ci] = (*cinfo->mem->alloc_sarray)
0N/A ((j_common_ptr) cinfo, JPOOL_IMAGE,
0N/A compptr->width_in_blocks * compptr->DCT_scaled_size,
0N/A (JDIMENSION) (rgroup * ngroups));
0N/A }
0N/A}