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