mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-12-05 12:05:22 +00:00
148 lines
5.0 KiB
C
148 lines
5.0 KiB
C
/*
|
|
* jdtrans.c
|
|
*
|
|
* Copyright (C) 1995-1997, 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 library routines for transcoding decompression,
|
|
* that is, reading raw DCT coefficient arrays from an input JPEG file.
|
|
* The routines in jdapimin.c will also be needed by a transcoder.
|
|
*/
|
|
|
|
#define JPEG_INTERNALS
|
|
#include "jinclude.h"
|
|
#include "jpeglib.h"
|
|
|
|
|
|
/* Forward declarations */
|
|
LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
|
|
|
|
|
|
/*
|
|
* Read the coefficient arrays from a JPEG file.
|
|
* jpeg_read_header must be completed before calling this.
|
|
*
|
|
* The entire image is read into a set of virtual coefficient-block arrays,
|
|
* one per component. The return value is a pointer to the array of
|
|
* virtual-array descriptors. These can be manipulated directly via the
|
|
* JPEG memory manager, or handed off to jpeg_write_coefficients().
|
|
* To release the memory occupied by the virtual arrays, call
|
|
* jpeg_finish_decompress() when done with the data.
|
|
*
|
|
* An alternative usage is to simply obtain access to the coefficient arrays
|
|
* during a buffered-image-mode decompression operation. This is allowed
|
|
* after any jpeg_finish_output() call. The arrays can be accessed until
|
|
* jpeg_finish_decompress() is called. (Note that any call to the library
|
|
* may reposition the arrays, so don't rely on access_virt_barray() results
|
|
* to stay valid across library calls.)
|
|
*
|
|
* Returns NULL if suspended. This case need be checked only if
|
|
* a suspending data source is used.
|
|
*/
|
|
|
|
GLOBAL(jvirt_barray_ptr *)
|
|
jpeg_read_coefficients (j_decompress_ptr cinfo)
|
|
{
|
|
if (cinfo->global_state == DSTATE_READY) {
|
|
/* First call: initialize active modules */
|
|
transdecode_master_selection(cinfo);
|
|
cinfo->global_state = DSTATE_RDCOEFS;
|
|
}
|
|
if (cinfo->global_state == DSTATE_RDCOEFS) {
|
|
/* Absorb whole file into the coef buffer */
|
|
for (;;) {
|
|
int retcode;
|
|
/* Call progress monitor hook if present */
|
|
if (cinfo->progress != NULL)
|
|
(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
|
|
/* Absorb some more input */
|
|
retcode = (*cinfo->inputctl->consume_input) (cinfo);
|
|
if (retcode == JPEG_SUSPENDED)
|
|
return NULL;
|
|
if (retcode == JPEG_REACHED_EOI)
|
|
break;
|
|
/* Advance progress counter if appropriate */
|
|
if (cinfo->progress != NULL &&
|
|
(retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
|
|
if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
|
|
/* startup underestimated number of scans; ratchet up one scan */
|
|
cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
|
|
}
|
|
}
|
|
}
|
|
/* Set state so that jpeg_finish_decompress does the right thing */
|
|
cinfo->global_state = DSTATE_STOPPING;
|
|
}
|
|
/* At this point we should be in state DSTATE_STOPPING if being used
|
|
* standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
|
|
* to the coefficients during a full buffered-image-mode decompression.
|
|
*/
|
|
if ((cinfo->global_state == DSTATE_STOPPING ||
|
|
cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
|
|
return cinfo->coef->coef_arrays;
|
|
}
|
|
/* Oops, improper usage */
|
|
ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
|
|
return NULL; /* keep compiler happy */
|
|
}
|
|
|
|
|
|
/*
|
|
* Master selection of decompression modules for transcoding.
|
|
* This substitutes for jdmaster.c's initialization of the full decompressor.
|
|
*/
|
|
|
|
LOCAL(void)
|
|
transdecode_master_selection (j_decompress_ptr cinfo)
|
|
{
|
|
/* This is effectively a buffered-image operation. */
|
|
cinfo->buffered_image = TRUE;
|
|
|
|
/* Entropy decoding: either Huffman or arithmetic coding. */
|
|
if (cinfo->arith_code) {
|
|
#ifdef D_ARITH_CODING_SUPPORTED
|
|
jinit_arith_decoder(cinfo);
|
|
#else
|
|
ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
|
|
#endif
|
|
} else {
|
|
if (cinfo->progressive_mode) {
|
|
#ifdef D_PROGRESSIVE_SUPPORTED
|
|
jinit_phuff_decoder(cinfo);
|
|
#else
|
|
ERREXIT(cinfo, JERR_NOT_COMPILED);
|
|
#endif
|
|
} else
|
|
jinit_huff_decoder(cinfo);
|
|
}
|
|
|
|
/* Always get a full-image coefficient buffer. */
|
|
jinit_d_coef_controller(cinfo, TRUE);
|
|
|
|
/* We can now tell the memory manager to allocate virtual arrays. */
|
|
(*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
|
|
|
|
/* Initialize input side of decompressor to consume first scan. */
|
|
(*cinfo->inputctl->start_input_pass) (cinfo);
|
|
|
|
/* Initialize progress monitoring. */
|
|
if (cinfo->progress != NULL) {
|
|
int nscans;
|
|
/* Estimate number of scans to set pass_limit. */
|
|
if (cinfo->progressive_mode) {
|
|
/* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
|
|
nscans = 2 + 3 * cinfo->num_components;
|
|
} else if (cinfo->inputctl->has_multiple_scans) {
|
|
/* For a nonprogressive multiscan file, estimate 1 scan per component. */
|
|
nscans = cinfo->num_components;
|
|
} else {
|
|
nscans = 1;
|
|
}
|
|
cinfo->progress->pass_counter = 0L;
|
|
cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
|
|
cinfo->progress->completed_passes = 0;
|
|
cinfo->progress->total_passes = 1;
|
|
}
|
|
}
|