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e8b40f3c
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2022-11-01T21:45:39
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Vastly improve 12-bit JPEG integration
The Gordian knot that 7fec5074f962b20ed00b4f5da4533e1e8d4ed8ac attempted
to unravel was caused by the fact that there are several
data-precision-dependent (JSAMPLE-dependent) fields and methods in the
exposed libjpeg API structures, and if you change the exposed libjpeg
API structures, then you have to change the whole API. If you change
the whole API, then you have to provide a whole new library to support
the new API, and that makes it difficult to support multiple data
precisions in the same application. (It is not impossible, as example.c
demonstrated, but using data-precision-dependent libjpeg API structures
would have made the cjpeg, djpeg, and jpegtran source code hard to read,
so it made more sense to build, install, and package 12-bit-specific
versions of those applications.)
Unfortunately, the result of that initial integration effort was an
unreadable and unmaintainable mess, which is a problem for a library
that is an ISO/ITU-T reference implementation. Also, as I dug into the
problem of lossless JPEG support, I realized that 16-bit lossless JPEG
images are a thing, and supporting yet another version of the libjpeg
API just for those images is untenable.
In fact, however, the touch points for JSAMPLE in the exposed libjpeg
API structures are minimal:
- The colormap and sample_range_limit fields in jpeg_decompress_struct
- The alloc_sarray() and access_virt_sarray() methods in
jpeg_memory_mgr
- jpeg_write_scanlines() and jpeg_write_raw_data()
- jpeg_read_scanlines() and jpeg_read_raw_data()
- jpeg_skip_scanlines() and jpeg_crop_scanline()
(This is subtle, but both of those functions use JSAMPLE-dependent
opaque structures behind the scenes.)
It is much more readable and maintainable to provide 12-bit-specific
versions of those six top-level API functions and to document that the
aforementioned methods and fields must be type-cast when using 12-bit
samples. Since that eliminates the need to provide a 12-bit-specific
version of the exposed libjpeg API structures, we can:
- Compile only the precision-dependent libjpeg modules (the
coefficient buffer controllers, the colorspace converters, the
DCT/IDCT managers, the main buffer controllers, the preprocessing
and postprocessing controller, the downsampler and upsamplers, the
quantizers, the integer DCT methods, and the IDCT methods) for
multiple data precisions.
- Introduce 12-bit-specific methods into the various internal
structures defined in jpegint.h.
- Create precision-independent data type, macro, method, field, and
function names that are prefixed by an underscore, and use an
internal header to convert those into precision-dependent data
type, macro, method, field, and function names, based on the value
of BITS_IN_JSAMPLE, when compiling the precision-dependent libjpeg
modules.
- Expose precision-dependent jinit*() functions for each of the
precision-dependent libjpeg modules.
- Abstract the precision-dependent libjpeg modules by calling the
appropriate precision-dependent jinit*() function, based on the
value of cinfo->data_precision, from top-level libjpeg API
functions.
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7fec5074
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2022-03-08T12:34:11
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Support 8-bit & 12-bit JPEGs using the same build
Partially implements #199
This commit also implements a request from #178 (the ability to compile
the libjpeg example as a standalone program.)
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01e30323
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2019-01-23T14:58:24
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Eliminate support for compilers w/o unsigned char
libjpeg-turbo has never really supported such compilers, since (AFAIK)
they are non-existent on any modern computing platform and thus
impossible for us to test. (Also, the TurboJPEG API would break without
unsigned chars.)
Furthermore, the unified CMake-based build system introduced in 2.0
always defines HAVE_UNSIGNED_CHAR, so retaining other code paths is
pointless. Eliminating support for compilers without unsigned char
eliminates the need for the GETJSAMPLE() macro, which improves the
readability of many parts of the code as well as improving the
performance of writing Targa and Windows BMP files.
Fixes #317
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a6289526
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2018-07-24T18:36:51
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Fix JPEG spec references per ISO/ITU-T suggestions
- When referring to specific clauses, annexes, tables, and figures, a
"timed reference" (a reference that includes the year) must be used in
order to avoid confusion.
- "CCITT" = "ITU-T"
- Replace ambiguous "JPEG spec" with the specific document number.
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da2a27ef
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2017-03-18T16:15:14
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Honor max_memory_to_use/JPEGMEM/-maxmemory
This re-introduces a feature of the obsolete system-specific libjpeg
memory managers-- namely the ability to limit the amount of main memory
used by the library during decompression or multi-pass compression.
This is mainly beneficial for two reasons:
- Works around a 2 GB limit in libFuzzer
- Allows security-sensitive applications to set a memory limit for the
JPEG decoder so as to work around the progressive JPEG exploit
(LJT-01-004) described here:
http://www.libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf
This commit also removes obsolete documentation regarding the MS-DOS
memory manager (which itself was removed long ago) and changes the
documentation of the -maxmemory switch and JPEGMEM environment variable
to reflect the fact that backing stores are never used in libjpeg-turbo.
Inspired by:
https://github.com/caolanm/libjpeg-turbo/commit/066fee2e7d6834f24838bc1896aa38ca77209e3c
Closes #143
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fc11193e
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2014-01-19T00:00:00
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The Independent JPEG Group's JPEG software v9a
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7e3acc0e
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2015-10-10T10:25:46
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Rename README, LICENSE, BUILDING text files
The IJG README file has been renamed to README.ijg, in order to avoid
confusion (many people were assuming that that was our project's README
file and weren't reading README-turbo.txt) and to lay the groundwork for
markdown versions of the libjpeg-turbo README and build instructions.
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5829cb23
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2012-01-15T00:00:00
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The Independent JPEG Group's JPEG software v8d
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5996a25e
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2009-06-27T00:00:00
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The Independent JPEG Group's JPEG software v7
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5033f3e1
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2014-05-18T18:33:44
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Remove MS-DOS code and information, and adjust copyright headers to reflect the removal of features in r1307 and r1308. libjpeg-turbo has never supported MS-DOS, nor is it even possible for us to do so.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1312 632fc199-4ca6-4c93-a231-07263d6284db
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da13af6b
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2014-05-18T17:52:06
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Further copyright header cleanup
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1310 632fc199-4ca6-4c93-a231-07263d6284db
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d88f7ddf
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2014-05-18T17:51:00
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Further copyright header cleanup
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1309 632fc199-4ca6-4c93-a231-07263d6284db
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b7753510
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2014-05-11T09:36:25
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Convert tabs to spaces in the libjpeg code and the SIMD code (TurboJPEG retains the use of tabs for historical reasons. They were annoying in the libjpeg code primarily because they were not consistently used and because they were used to format as well as indent the code. In the case of TurboJPEG, tabs are used just to indent the code, so even if the editor assumes a different tab width, the code will still be readable.)
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1285 632fc199-4ca6-4c93-a231-07263d6284db
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e5eaf374
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2014-05-09T18:00:32
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Convert tabs to spaces in the libjpeg code and the SIMD code (TurboJPEG retains the use of tabs for historical reasons. They were annoying in the libjpeg code primarily because they were not consistently used and because they were used to format as well as indent the code. In the case of TurboJPEG, tabs are used just to indent the code, so even if the editor assumes a different tab width, the code will still be readable.)
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1278 632fc199-4ca6-4c93-a231-07263d6284db
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a73e870a
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2012-12-31T02:52:30
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Change the copyright notices to make it clear that our modified files are not part of the IJG's software.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.2.x@873 632fc199-4ca6-4c93-a231-07263d6284db
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0bfb7805
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2012-12-31T02:42:18
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Change the copyright notices to make it clear that our modified files are not part of the IJG's software.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@872 632fc199-4ca6-4c93-a231-07263d6284db
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760ea8df
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2012-02-07T23:25:19
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Merge documentation and wordsmithing changes from 1.2, including promotion of -arithmetic to a "switch for advanced users"
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.1.x@783 632fc199-4ca6-4c93-a231-07263d6284db
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66a69f04
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2012-01-31T10:19:29
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Incorporate a few upstream doc changes; grammar police; wordsmithing; Move -arithmetic into "switches for advanced users"; Additional documentation for IDCT scaling extensions
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@765 632fc199-4ca6-4c93-a231-07263d6284db
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ccd1bfdd
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2012-01-31T09:53:46
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Incorporate a few upstream doc changes; grammar police; wordsmithing; Move -arithmetic into "switches for advanced users"
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.2.x@764 632fc199-4ca6-4c93-a231-07263d6284db
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66f97e68
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2010-11-23T05:49:54
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Support arithmetic encoding and decoding
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@299 632fc199-4ca6-4c93-a231-07263d6284db
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39ea562c
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2010-10-12T01:55:31
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Document new v7/v8 features; .doc = .txt
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@252 632fc199-4ca6-4c93-a231-07263d6284db
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