opencv/3rdparty/libjpeg-turbo/src/jchuff.h
Alexander Smorkalov d97df262f6
Merge pull request #25623 from asmorkalov:as/jpegturbo_3.0.3
Libjpeg-turbo update to version 3.0.3 #25623

### Pull Request Readiness Checklist

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- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
2024-05-25 13:03:12 +03:00

45 lines
1.7 KiB
C

/*
* jchuff.h
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains declarations for Huffman entropy encoding routines
* that are shared between the sequential encoder (jchuff.c) and the
* progressive encoder (jcphuff.c). No other modules need to see these.
*/
/* The legal range of a DCT coefficient is
* -1024 .. +1023 for 8-bit data;
* -16384 .. +16383 for 12-bit data.
* Hence the magnitude should always fit in 10 or 14 bits respectively.
*/
/* The progressive Huffman encoder uses an unsigned 16-bit data type to store
* absolute values of coefficients, because it is possible to inject a
* coefficient value of -32768 into the encoder by attempting to transform a
* malformed 12-bit JPEG image, and the absolute value of -32768 would overflow
* a signed 16-bit integer.
*/
typedef unsigned short UJCOEF;
/* Derived data constructed for each Huffman table */
typedef struct {
unsigned int ehufco[256]; /* code for each symbol */
char ehufsi[256]; /* length of code for each symbol */
/* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
} c_derived_tbl;
/* Expand a Huffman table definition into the derived format */
EXTERN(void) jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC,
int tblno, c_derived_tbl **pdtbl);
/* Generate an optimal table definition given the specified counts */
EXTERN(void) jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl,
long freq[]);