www.pudn.com > Cimage.zip > JDCOEFCT.C
/*
* jdcoefct.c
*
* Copyright (C) 1994, 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 decompression.
* This controller is the top level of the JPEG decompressor proper.
* The coefficient buffer lies between entropy decoding and inverse-DCT steps.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
/* Private buffer controller object */
typedef struct {
struct jpeg_d_coef_controller pub; /* public fields */
JDIMENSION MCU_col_num; /* saves next MCU column to process */
JDIMENSION MCU_row_num; /* keep track of MCU row # within image */
/* In single-pass modes without block smoothing, it's sufficient to buffer
* just one MCU (although this may prove a bit slow in practice).
* We allocate a workspace of MAX_BLOCKS_IN_MCU coefficient blocks,
* and let the entropy decoder write into that workspace each time.
* (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[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 decompress_data
JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#ifdef D_MULTISCAN_FILES_SUPPORTED
METHODDEF boolean decompress_read
JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
METHODDEF boolean decompress_output
JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#endif
/*
* Initialize for a processing pass.
*/
METHODDEF void
start_pass_coef (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
{
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
coef->MCU_col_num = 0;
coef->MCU_row_num = 0;
switch (pass_mode) {
case JBUF_PASS_THRU:
if (coef->whole_image[0] != NULL)
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
coef->pub.decompress_data = decompress_data;
break;
#ifdef D_MULTISCAN_FILES_SUPPORTED
case JBUF_SAVE_SOURCE:
if (coef->whole_image[0] == NULL)
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
coef->pub.decompress_data = decompress_read;
break;
case JBUF_CRANK_DEST:
if (coef->whole_image[0] == NULL)
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
coef->pub.decompress_data = decompress_output;
break;
#endif
default:
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
break;
}
}
/*
* Process some data in the single-pass case.
* Always attempts to emit one fully interleaved MCU row ("iMCU" row).
* Returns TRUE if it completed a row, FALSE if not (suspension).
*
* NB: output_buf contains a plane for each component in image.
* For single pass, this is the same as the components in the scan.
*/
METHODDEF boolean
decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_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_MCU_row = cinfo->MCU_rows_in_scan - 1;
int blkn, ci, xindex, yindex, useful_width;
JSAMPARRAY output_ptr;
JDIMENSION start_col, output_col;
jpeg_component_info *compptr;
inverse_DCT_method_ptr inverse_DCT;
/* Loop to process as much as one whole MCU row */
for (MCU_col_num = coef->MCU_col_num; MCU_col_num <= last_MCU_col;
MCU_col_num++) {
/* Try to fetch an MCU. Entropy decoder expects buffer to be zeroed. */
jzero_far((void FAR *) coef->MCU_buffer[0],
(size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
/* Suspension forced; return with row unfinished */
coef->MCU_col_num = MCU_col_num; /* update my state */
return FALSE;
}
/* Determine where data should go in output_buf and do the IDCT thing.
* We skip dummy blocks at the right and bottom edges (but blkn gets
* incremented past them!). Note the inner loop relies on having
* allocated the MCU_buffer[] blocks sequentially.
*/
blkn = 0; /* index of current DCT block within MCU */
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
compptr = cinfo->cur_comp_info[ci];
/* Don't bother to IDCT an uninteresting component. */
if (! compptr->component_needed) {
blkn += compptr->MCU_blocks;
continue;
}
inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
: compptr->last_col_width;
output_ptr = output_buf[ci];
start_col = MCU_col_num * compptr->MCU_sample_width;
for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
if (coef->MCU_row_num < last_MCU_row ||
yindex < compptr->last_row_height) {
output_col = start_col;
for (xindex = 0; xindex < useful_width; xindex++) {
(*inverse_DCT) (cinfo, compptr,
(JCOEFPTR) coef->MCU_buffer[blkn+xindex],
output_ptr, output_col);
output_col += compptr->DCT_scaled_size;
}
}
blkn += compptr->MCU_width;
output_ptr += compptr->DCT_scaled_size;
}
}
}
/* We finished the row successfully */
coef->MCU_col_num = 0; /* prepare for next row */
coef->MCU_row_num++;
return TRUE;
}
#ifdef D_MULTISCAN_FILES_SUPPORTED
/*
* Process some data: handle an input pass for a multiple-scan file.
* We read the equivalent of one fully interleaved MCU row ("iMCU" row)
* per call, ie, v_samp_factor block rows for each component in the scan.
* No data is returned; we just stash it in the virtual arrays.
*
* Returns TRUE if it completed a row, FALSE if not (suspension).
* Currently, the suspension case is not supported.
*/
METHODDEF boolean
decompress_read (j_decompress_ptr cinfo, JSAMPIMAGE output_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, num_MCU_rows;
JDIMENSION total_width, remaining_rows, 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. */
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->MCU_row_num * compptr->v_samp_factor, TRUE);
/* Entropy decoder expects buffer to be zeroed. */
total_width = (JDIMENSION) jround_up((long) compptr->width_in_blocks,
(long) compptr->h_samp_factor);
for (yindex = 0; yindex < compptr->v_samp_factor; yindex++) {
jzero_far((void FAR *) buffer[ci][yindex],
(size_t) (total_width * SIZEOF(JBLOCK)));
}
}
/* In an interleaved scan, we process exactly one MCU row.
* In a noninterleaved scan, we need to process v_samp_factor MCU rows,
* each of which contains a single block row.
*/
if (cinfo->comps_in_scan == 1) {
compptr = cinfo->cur_comp_info[0];
num_MCU_rows = compptr->v_samp_factor;
/* but watch out for the bottom of the image */
remaining_rows = cinfo->MCU_rows_in_scan -
coef->MCU_row_num * compptr->v_samp_factor;
if (remaining_rows < (JDIMENSION) num_MCU_rows)
num_MCU_rows = (int) remaining_rows;
} else {
num_MCU_rows = 1;
}
/* Loop to process one whole iMCU row */
for (yoffset = 0; yoffset < num_MCU_rows; yoffset++) {
for (MCU_col_num = 0; 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 fetch the MCU. */
if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
ERREXIT(cinfo, JERR_CANT_SUSPEND); /* not supported */
}
}
}
coef->MCU_row_num++;
return TRUE;
}
/*
* Process some data: output from the virtual arrays after reading is done.
* Always emits one fully interleaved MCU row ("iMCU" row).
* Always returns TRUE --- suspension is not possible.
*
* NB: output_buf contains a plane for each component in image.
*/
METHODDEF boolean
decompress_output (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
JDIMENSION last_MCU_row = cinfo->total_iMCU_rows - 1;
JDIMENSION block_num;
int ci, block_row, block_rows;
JBLOCKARRAY buffer;
JBLOCKROW buffer_ptr;
JSAMPARRAY output_ptr;
JDIMENSION output_col;
jpeg_component_info *compptr;
inverse_DCT_method_ptr inverse_DCT;
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
/* Don't bother to IDCT an uninteresting component. */
if (! compptr->component_needed)
continue;
/* Align the virtual buffer for this component. */
buffer = (*cinfo->mem->access_virt_barray)
((j_common_ptr) cinfo, coef->whole_image[ci],
coef->MCU_row_num * compptr->v_samp_factor, FALSE);
/* Count non-dummy DCT block rows in this iMCU row. */
if (coef->MCU_row_num < last_MCU_row)
block_rows = compptr->v_samp_factor;
else {
block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
if (block_rows == 0) block_rows = compptr->v_samp_factor;
}
inverse_DCT = cinfo->idct->inverse_DCT[ci];
output_ptr = output_buf[ci];
/* Loop over all DCT blocks to be processed. */
for (block_row = 0; block_row < block_rows; block_row++) {
buffer_ptr = buffer[block_row];
output_col = 0;
for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
output_ptr, output_col);
buffer_ptr++;
output_col += compptr->DCT_scaled_size;
}
output_ptr += compptr->DCT_scaled_size;
}
}
coef->MCU_row_num++;
return TRUE;
}
#endif /* D_MULTISCAN_FILES_SUPPORTED */
/*
* Initialize coefficient buffer controller.
*/
GLOBAL void
jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
{
my_coef_ptr coef;
int ci, i;
jpeg_component_info *compptr;
JBLOCKROW buffer;
coef = (my_coef_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
SIZEOF(my_coef_controller));
cinfo->coef = (struct jpeg_d_coef_controller *) coef;
coef->pub.start_pass = start_pass_coef;
/* Create the coefficient buffer. */
if (need_full_buffer) {
#ifdef D_MULTISCAN_FILES_SUPPORTED
/* Allocate a full-image virtual array for each component, */
/* padded to a multiple of samp_factor DCT blocks in each direction. */
/* Note memmgr implicitly pads the vertical direction. */
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,
(JDIMENSION) jround_up((long) compptr->width_in_blocks,
(long) compptr->h_samp_factor),
compptr->height_in_blocks,
(JDIMENSION) compptr->v_samp_factor);
}
#else
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
} else {
/* We only need a single-MCU buffer. */
buffer = (JBLOCKROW)
(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
for (i = 0; i < MAX_BLOCKS_IN_MCU; i++) {
coef->MCU_buffer[i] = buffer + i;
}
coef->whole_image[0] = NULL; /* flag for no virtual arrays */
}
}