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