ref: bea7b7bf8ccbc2bc41906517079e76fcfb31cb5a
dir: /code/jpeg-6/jdpostct.c/
/*
* jdpostct.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 decompression postprocessing controller.
* This controller manages the upsampling, color conversion, and color
* quantization/reduction steps; specifically, it controls the buffering
* between upsample/color conversion and color quantization/reduction.
*
* If no color quantization/reduction is required, then this module has no
* work to do, and it just hands off to the upsample/color conversion code.
* An integrated upsample/convert/quantize process would replace this module
* entirely.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
/* Private buffer controller object */
typedef struct {
struct jpeg_d_post_controller pub; /* public fields */
/* Color quantization source buffer: this holds output data from
* the upsample/color conversion step to be passed to the quantizer.
* For two-pass color quantization, we need a full-image buffer;
* for one-pass operation, a strip buffer is sufficient.
*/
jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
JSAMPARRAY buffer; /* strip buffer, or current strip of virtual */
JDIMENSION strip_height; /* buffer size in rows */
/* for two-pass mode only: */
JDIMENSION starting_row; /* row # of first row in current strip */
JDIMENSION next_row; /* index of next row to fill/empty in strip */
} my_post_controller;
typedef my_post_controller * my_post_ptr;
/* Forward declarations */
METHODDEF void post_process_1pass
JPP((j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail));
#ifdef QUANT_2PASS_SUPPORTED
METHODDEF void post_process_prepass
JPP((j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail));
METHODDEF void post_process_2pass
JPP((j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail));
#endif
/*
* Initialize for a processing pass.
*/
METHODDEF void
start_pass_dpost (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
{
my_post_ptr post = (my_post_ptr) cinfo->post;
switch (pass_mode) {
case JBUF_PASS_THRU:
if (cinfo->quantize_colors) {
/* Single-pass processing with color quantization. */
post->pub.post_process_data = post_process_1pass;
/* We could be doing buffered-image output before starting a 2-pass
* color quantization; in that case, jinit_d_post_controller did not
* allocate a strip buffer. Use the virtual-array buffer as workspace.
*/
if (post->buffer == NULL) {
post->buffer = (*cinfo->mem->access_virt_sarray)
((j_common_ptr) cinfo, post->whole_image,
(JDIMENSION) 0, post->strip_height, TRUE);
}
} else {
/* For single-pass processing without color quantization,
* I have no work to do; just call the upsampler directly.
*/
post->pub.post_process_data = cinfo->upsample->upsample;
}
break;
#ifdef QUANT_2PASS_SUPPORTED
case JBUF_SAVE_AND_PASS:
/* First pass of 2-pass quantization */
if (post->whole_image == NULL)
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
post->pub.post_process_data = post_process_prepass;
break;
case JBUF_CRANK_DEST:
/* Second pass of 2-pass quantization */
if (post->whole_image == NULL)
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
post->pub.post_process_data = post_process_2pass;
break;
#endif /* QUANT_2PASS_SUPPORTED */
default:
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
break;
}
post->starting_row = post->next_row = 0;
}
/*
* Process some data in the one-pass (strip buffer) case.
* This is used for color precision reduction as well as one-pass quantization.
*/
METHODDEF void
post_process_1pass (j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail)
{
my_post_ptr post = (my_post_ptr) cinfo->post;
JDIMENSION num_rows, max_rows;
/* Fill the buffer, but not more than what we can dump out in one go. */
/* Note we rely on the upsampler to detect bottom of image. */
max_rows = out_rows_avail - *out_row_ctr;
if (max_rows > post->strip_height)
max_rows = post->strip_height;
num_rows = 0;
(*cinfo->upsample->upsample) (cinfo,
input_buf, in_row_group_ctr, in_row_groups_avail,
post->buffer, &num_rows, max_rows);
/* Quantize and emit data. */
(*cinfo->cquantize->color_quantize) (cinfo,
post->buffer, output_buf + *out_row_ctr, (int) num_rows);
*out_row_ctr += num_rows;
}
#ifdef QUANT_2PASS_SUPPORTED
/*
* Process some data in the first pass of 2-pass quantization.
*/
METHODDEF void
post_process_prepass (j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail)
{
my_post_ptr post = (my_post_ptr) cinfo->post;
JDIMENSION old_next_row, num_rows;
/* Reposition virtual buffer if at start of strip. */
if (post->next_row == 0) {
post->buffer = (*cinfo->mem->access_virt_sarray)
((j_common_ptr) cinfo, post->whole_image,
post->starting_row, post->strip_height, TRUE);
}
/* Upsample some data (up to a strip height's worth). */
old_next_row = post->next_row;
(*cinfo->upsample->upsample) (cinfo,
input_buf, in_row_group_ctr, in_row_groups_avail,
post->buffer, &post->next_row, post->strip_height);
/* Allow quantizer to scan new data. No data is emitted, */
/* but we advance out_row_ctr so outer loop can tell when we're done. */
if (post->next_row > old_next_row) {
num_rows = post->next_row - old_next_row;
(*cinfo->cquantize->color_quantize) (cinfo, post->buffer + old_next_row,
(JSAMPARRAY) NULL, (int) num_rows);
*out_row_ctr += num_rows;
}
/* Advance if we filled the strip. */
if (post->next_row >= post->strip_height) {
post->starting_row += post->strip_height;
post->next_row = 0;
}
}
/*
* Process some data in the second pass of 2-pass quantization.
*/
METHODDEF void
post_process_2pass (j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
JDIMENSION in_row_groups_avail,
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
JDIMENSION out_rows_avail)
{
my_post_ptr post = (my_post_ptr) cinfo->post;
JDIMENSION num_rows, max_rows;
/* Reposition virtual buffer if at start of strip. */
if (post->next_row == 0) {
post->buffer = (*cinfo->mem->access_virt_sarray)
((j_common_ptr) cinfo, post->whole_image,
post->starting_row, post->strip_height, FALSE);
}
/* Determine number of rows to emit. */
num_rows = post->strip_height - post->next_row; /* available in strip */
max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
if (num_rows > max_rows)
num_rows = max_rows;
/* We have to check bottom of image here, can't depend on upsampler. */
max_rows = cinfo->output_height - post->starting_row;
if (num_rows > max_rows)
num_rows = max_rows;
/* Quantize and emit data. */
(*cinfo->cquantize->color_quantize) (cinfo,
post->buffer + post->next_row, output_buf + *out_row_ctr,
(int) num_rows);
*out_row_ctr += num_rows;
/* Advance if we filled the strip. */
post->next_row += num_rows;
if (post->next_row >= post->strip_height) {
post->starting_row += post->strip_height;
post->next_row = 0;
}
}
#endif /* QUANT_2PASS_SUPPORTED */
/*
* Initialize postprocessing controller.
*/
GLOBAL void
jinit_d_post_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
{
my_post_ptr post;
post = (my_post_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
SIZEOF(my_post_controller));
cinfo->post = (struct jpeg_d_post_controller *) post;
post->pub.start_pass = start_pass_dpost;
post->whole_image = NULL; /* flag for no virtual arrays */
post->buffer = NULL; /* flag for no strip buffer */
/* Create the quantization buffer, if needed */
if (cinfo->quantize_colors) {
/* The buffer strip height is max_v_samp_factor, which is typically
* an efficient number of rows for upsampling to return.
* (In the presence of output rescaling, we might want to be smarter?)
*/
post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
if (need_full_buffer) {
/* Two-pass color quantization: need full-image storage. */
/* We round up the number of rows to a multiple of the strip height. */
#ifdef QUANT_2PASS_SUPPORTED
post->whole_image = (*cinfo->mem->request_virt_sarray)
((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
cinfo->output_width * cinfo->out_color_components,
(JDIMENSION) jround_up((long) cinfo->output_height,
(long) post->strip_height),
post->strip_height);
#else
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif /* QUANT_2PASS_SUPPORTED */
} else {
/* One-pass color quantization: just make a strip buffer. */
post->buffer = (*cinfo->mem->alloc_sarray)
((j_common_ptr) cinfo, JPOOL_IMAGE,
cinfo->output_width * cinfo->out_color_components,
post->strip_height);
}
}
}