af618ffe09
- Rename jpeg_simple_lossless() to jpeg_enable_lossless() and modify the
function so that it stores the lossless parameters directly in the Ss
and Al fields of jpeg_compress_struct rather than using a scan script.
- Move the cjpeg -lossless switch into "Switches for advanced users".
- Document the libjpeg API and run-time features that are unavailable in
lossless mode, and ensure that all parameters, functions, and switches
related to unavailable features are ignored or generate errors in
lossless mode.
- Defer any action that depends on whether lossless mode is enabled
until jpeg_start_compress()/jpeg_start_decompress() is called.
- Document the purpose of the point transform value.
- "Codec" stands for coder/decoder, so it is a bit awkward to say
"lossless compression codec" and "lossless decompression codec".
Use "lossless compressor" and "lossless decompressor" instead.
- Restore backward API/ABI compatibility with libjpeg v6b:
* Move the new 'lossless' field from the exposed jpeg_compress_struct
and jpeg_decompress_struct structures into the opaque
jpeg_comp_master and jpeg_decomp_master structures, and allocate the
master structures in the body of jpeg_create_compress() and
jpeg_create_decompress().
* Remove the new 'process' field from jpeg_compress_struct and
jpeg_decompress_struct and replace it with the old
'progressive_mode' field and the new 'lossless' field.
* Remove the new 'data_unit' field from jpeg_compress_struct and
jpeg_decompress_struct and replace it with a locally-computed
data unit variable.
* Restore the names of macros and fields that refer to DCT blocks, and
document that they have a different meaning in lossless mode. (Most
of them aren't very meaningful in lossless mode anyhow.)
* Remove the new alloc_darray() method from jpeg_memory_mgr and
replace it with an internal macro that wraps the alloc_sarray()
method.
* Move the JDIFF* data types from jpeglib.h and jmorecfg.h into
jpegint.h.
* Remove the new 'codec' field from jpeg_compress_struct and
jpeg_decompress_struct and instead reuse the existing internal
coefficient control, forward/inverse DCT, and entropy
encoding/decoding structures for lossless compression/decompression.
* Repurpose existing error codes rather than introducing new ones.
(The new JERR_BAD_RESTART and JWRN_MUST_DOWNSCALE codes remain,
although JWRN_MUST_DOWNSCALE will probably be removed in
libjpeg-turbo, since we have a different way of handling multiple
data precisions.)
- Automatically enable lossless mode when a scan script with parameters
that are only valid for lossless mode is detected, and document the
use of scan scripts to generate lossless JPEG images.
- Move the sequential and shared Huffman routines back into jchuff.c and
jdhuff.c, and document that those routines are shared with jclhuff.c
and jdlhuff.c as well as with jcphuff.c and jdphuff.c.
- Move MAX_DIFF_BITS from jchuff.h into jclhuff.c, the only place where
it is used.
- Move the predictor and scaler code into jclossls.c and jdlossls.c.
- Streamline register usage in the [un]differencers (inspired by similar
optimizations in the color [de]converters.)
- Restructure the logic in a few places to reduce duplicated code.
- Ensure that all lossless-specific code is guarded by
C_LOSSLESS_SUPPORTED or D_LOSSLESS_SUPPORTED and that the library can
be built successfully if either or both of those macros is undefined.
- Remove all short forms of external names introduced by the lossless
JPEG patch. (These will not be needed by libjpeg-turbo, so there is
no use cleaning them up.)
- Various wordsmithing, formatting, and punctuation tweaks
- Eliminate various compiler warnings.
97 lines
3.0 KiB
C
97 lines
3.0 KiB
C
/*
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* jcinit.c
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*
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* This file was part of the Independent JPEG Group's software:
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* Copyright (C) 1991-1997, Thomas G. Lane.
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* Lossless JPEG Modifications:
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* Copyright (C) 1999, Ken Murchison.
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* Copyright (C) 2022, D. R. Commander.
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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 initialization logic for the JPEG compressor.
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* This routine is in charge of selecting the modules to be executed and
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* making an initialization call to each one.
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*
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* Logically, this code belongs in jcmaster.c. It's split out because
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* linking this routine implies linking the entire compression library.
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* For a transcoding-only application, we want to be able to use jcmaster.c
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* without linking in the whole library.
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*/
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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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/*
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* Master selection of compression modules.
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* This is done once at the start of processing an image. We determine
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* which modules will be used and give them appropriate initialization calls.
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*/
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GLOBAL(void)
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jinit_compress_master (j_compress_ptr cinfo)
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{
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/* Initialize master control (includes parameter checking/processing) */
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jinit_c_master_control(cinfo, FALSE /* full compression */);
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/* Preprocessing */
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if (! cinfo->raw_data_in) {
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jinit_color_converter(cinfo);
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jinit_downsampler(cinfo);
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jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
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}
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if (cinfo->master->lossless) {
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#ifdef C_LOSSLESS_SUPPORTED
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/* Prediction, sample differencing, and point transform */
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jinit_lossless_compressor(cinfo);
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/* Entropy encoding: either Huffman or arithmetic coding. */
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if (cinfo->arith_code) {
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ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
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} else {
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jinit_lhuff_encoder(cinfo);
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}
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/* Need a full-image difference buffer in any multi-pass mode. */
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jinit_c_diff_controller(cinfo,
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(boolean) (cinfo->num_scans > 1 || cinfo->optimize_coding));
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#else
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif
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} else {
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/* Forward DCT */
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jinit_forward_dct(cinfo);
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/* Entropy encoding: either Huffman or arithmetic coding. */
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if (cinfo->arith_code) {
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ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
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} else {
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if (cinfo->progressive_mode) {
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#ifdef C_PROGRESSIVE_SUPPORTED
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jinit_phuff_encoder(cinfo);
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#else
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ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif
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} else
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jinit_huff_encoder(cinfo);
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}
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/* Need a full-image coefficient buffer in any multi-pass mode. */
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jinit_c_coef_controller(cinfo,
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(boolean) (cinfo->num_scans > 1 || cinfo->optimize_coding));
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}
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jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);
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jinit_marker_writer(cinfo);
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/* We can now tell the memory manager to allocate virtual arrays. */
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(*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
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/* Write the datastream header (SOI) immediately.
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* Frame and scan headers are postponed till later.
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* This lets application insert special markers after the SOI.
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*/
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(*cinfo->marker->write_file_header) (cinfo);
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}
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