|
9e17440a
|
2025-11-10T18:49:38
|
|
Doc: Wordsmithing
|
|
|
466c3448
|
2025-10-23T10:41:16
|
|
TurboJPEG doc tweaks
- Clarify that YUV encoding performs downsampling as well as color
conversion.
- Clarify that TJPARAM_LOSSLESS is ignored by tj3CompressFromYUV*8().
- Clarify that tj3CompressFromYUV*8() generates only YCbCr or grayscale
JPEG images, i.e. that TJPARAM_COLORSPACE has no effect.
|
|
|
6d48aaac
|
2025-10-22T10:30:53
|
|
TJ: Handle lossless/CS params w/ YUV enc/compress
- If TJPARAM_LOSSLESS was set, then tj3EncodeYUV*8() called
jpeg_enable_lossless() (via setCompDefaults()), which caused the
underlying libjpeg API to silently disable subsampling and color
conversion. This led to three issues:
1. Attempting to encode RGB pixels produced incorrect YCbCr or
grayscale components, since color conversion did not occur. The
same issue occurred if TJPARAM_COLORSPACE was explicitly set to
TJCS_RGB.
2. Attempting to encode RGB pixels into a grayscale plane caused
tj3EncodeYUVPlanes8() to overflow the caller's destination pointer
array if the array was not big enough to accommodate three
pointers. If called from tj3EncodeYUV8(), tj3EncodeYUVPlanes8()
did not overflow the caller's destination pointer array, but a
segfault occurred when it attempted to copy to the Cb and Cr
pointers, which were NULL. The same issue occurred if
TJPARAM_COLORSPACE was explicitly set to anything other than
TJCS_GRAY.
3. Attempting to encode RGB pixels into subsampled YUV planes caused
tj3EncodeYUV*8() to overflow the caller's buffer(s) if the
buffer(s) were not big enough to accommodate 4:4:4 (non-subsampled)
YUV planes. That would have been the case if the caller allocated
its buffer(s) based on the return value of tj3YUVBufSize() or
tj3YUVPlaneSize(). The same issue occurs if TJPARAM_SUBSAMP is
explicitly set to TJSAMP_444.
tj3EncodeYUV*8() now ignores TJPARAM_LOSSLESS and TJPARAM_COLORSPACE.
- If TJPARAM_LOSSLESS was set, then attempting to compress a grayscale
plane into a JPEG image caused tj3CompressFromYUVPlanes8() to overflow
the caller's source pointer array if the array was not big enough to
accommodate three pointers. If called from tj3CompressFromYUV8(),
tj3CompressFromYUVPlanes8() did not overflow the caller's source
pointer array, but a segfault occurred when it attempted to copy from
the Cb and Cr pointers, which were NULL. This was similar to Issue 2
above. The same issue occurred if TJPARAM_COLORSPACE was explicitly
set to anything other than TJCS_GRAY.
tj3CompressFromYUV*8() now throws an error if TJPARAM_LOSSLESS is set,
and it now ignores TJPARAM_COLORSPACE.
These issues did not pose a security risk, since security exploits
involve supported workflows that function normally except when supplied
with malformed input data. It is documented that colorspace conversion,
chrominance subsampling, and compression from planar YUV images are
unavailable when TJPARAM_LOSSLESS is set. When TJPARAM_LOSSLESS is set,
the library effectively sets TJPARAM_SUBSAMP to TJSAMP_444 and
TJPARAM_COLORSPACE to TJCS_RGB, TJCS_GRAY, or TJCS_CMYK, depending on
the pixel format of the source image. That behavior is strongly implied
by the documentation of TJPARAM_LOSSLESS, although the documentation
isn't specific about whether TJPARAM_LOSSLESS applies to
tj3EncodeYUV*8(). In any case, setting TJPARAM_LOSSLESS before calling
tj3CompressFromYUV*8() was never a supported or functional workflow, and
setting TJPARAM_LOSSLESS before calling tj3EncodeYUV*8() was never a
functional workflow. Thus, there should be no applications "in the
wild" that use either workflow. Such applications would crash every
time they attempted to encode to or compress from a YUV image. In other
words, setting TJPARAM_LOSSLESS or TJPARAM_COLORSPACE required the
caller to understand the ramifications of the loss of color conversion
and/or subsampling, and failing to do so was essentially API abuse
(albeit subtle API abuse, hence the desire to make the behavior more
intuitive.)
This commit also removes no-op code introduced by
6da05150efa9b7a190d05bf82295127c778d15ab. Since setCompDefaults()
returns after calling jpeg_enable_lossless(), modifying the subsampling
level locally had no effect. The libjpeg API already silently disables
subsampling in jinit_c_master_control() if lossless compression is
enabled, so it was not necessary for setCompDefaults() to handle that.
Fixes #839
|
|
|
d7932a27
|
2024-10-30T12:12:03
|
|
TJ doc: Density params require YCbCr or grayscale
Since libjpeg-turbo does not support Exif, the only way it can embed
density information in a JPEG image is by using the JFIF marker, which
is only written if the JPEG colorspace is YCbCr or grayscale.
(Referring to the conversation under #793, we may need to further
restrict that to 8-bit-per-sample JPEG images, because the JFIF spec
requires 8-bit data precision.)
|
|
|
9b01f5a0
|
2024-09-14T11:56:14
|
|
TJ: Add func/method for computing xformed buf size
|
|
|
a2728582
|
2024-09-03T07:54:17
|
|
TurboJPEG: ICC profile support
|
|
|
c519d7b6
|
2024-09-05T11:10:44
|
|
Don't ignore JPEG buf size with TJPARAM_NOREALLOC
Since the introduction of TJFLAG_NOREALLOC in libjpeg-turbo 1.2.x, the
TurboJPEG C API documentation has (confusingly) stated that:
- if the JPEG buffer pointer points to a pre-allocated buffer, then the
JPEG buffer size must be specified, and
- the JPEG buffer size should be specified if the JPEG buffer is
pre-allocated to an arbitrary size.
The documentation never explicitly stated that the JPEG buffer size
should be specified if the JPEG buffer is pre-allocated to a worst-case
size, but since focus does not imply exclusion, it also never explicitly
stated the reverse. Furthermore, the documentation never stated that
this was contingent upon TJPARAM_NOREALLOC/TJFLAG_NOREALLOC. However,
effectively the compression and lossless transformation functions
ignored the JPEG buffer size(s) passed to them, and assumed that the
JPEG buffer(s) had been allocated to a worst-case size, if
TJPARAM_NOREALLOC/TJFLAG_NOREALLOC was set. This behavior was an
accidental and undocumented throwback to libjpeg-turbo 1.1.x, in which
the tjCompress() function provided no way to specify the JPEG buffer
size. It was always a bad idea for applications to rely upon that
behavior (although our own TJBench application unfortunately did.)
However, if such applications exist in the wild, the new behavior would
constitute a breaking change, so it has been introduced only into
libjpeg-turbo 3.1.x and only into TurboJPEG 3 API functions. The
previous behavior has been retained when calling functions from the
TurboJPEG 2.1.x API and prior versions.
Did I mention that APIs are hard?
|
|
|
5f05c75a
|
2024-09-06T19:55:20
|
|
Merge branch 'main' into dev
|
|
|
a4d19a45
|
2024-09-03T09:27:04
|
|
Merge branch 'main' into dev
|
|
|
6d9f1f81
|
2024-09-01T14:04:20
|
|
Merge branch 'main' into dev
|
|
|
64567381
|
2024-08-31T17:31:02
|
|
Merge branch 'main' into dev
|
|
|
fd9b21b6
|
2024-08-28T18:58:21
|
|
Merge branch 'main' into dev
|
|
|
6a9565ce
|
2024-08-26T16:45:41
|
|
Merge branch 'main' into dev
|
|
|
26d978b6
|
2024-08-16T11:58:02
|
|
Merge branch 'main' into dev
|
|
|
6ec8e41f
|
2024-06-13T11:52:13
|
|
Handle lossless JPEG images w/2-15 bits per sample
Closes #768
Closes #769
|
|
|
e69dd40c
|
2024-01-23T13:26:41
|
|
Reorganize source to make things easier to find
- Move all libjpeg documentation, except for README.ijg, into the doc/
subdirectory.
- Move the TurboJPEG C API documentation from doc/html/ into
doc/turbojpeg/.
- Move all C source code and headers into a src/ subdirectory.
- Move turbojpeg-jni.c into the java/ subdirectory.
Referring to #226, there is no ideal solution to this problem. A
semantically ideal solution would have involved placing all source code,
including the SIMD and Java source code, under src/ (or perhaps placing
C library source code under lib/ and C test program source code under
test/), all header files under include/, and all documentation under
doc/. However:
- To me it makes more sense to have separate top-level directories for
each language, since the SIMD extensions and the Java API are
technically optional features. src/ now contains only the code that
is relevant to the core C API libraries and associated programs.
- I didn't want to bury the java/ and simd/ directories or add a level
of depth to them, since both directories already contain source code
that is 3-4 levels deep.
- I would prefer not to separate the header files from the C source
code, because:
1. It would be disruptive. libjpeg and libjpeg-turbo have
historically placed C source code and headers in the same
directory, and people who are familiar with both projects (self
included) are used to looking for the headers in the same directory
as the C source code.
2. In terms of how the headers are used internally in libjpeg-turbo,
the distinction between public and private headers is a bit fuzzy.
- It didn't make sense to separate the test source code from the library
source code, since there is not a clear distinction in some cases.
(For instance, the IJG image I/O functions are used by cjpeg and djpeg
as well as by the TurboJPEG API.)
This solution is minimally disruptive, since it keeps all C source code
and headers together and keeps java/ and simd/ as top-level directories.
It is a bit awkward, because java/ and simd/ technically contain source
code, even though they are not under src/. However, other solutions
would have been more awkward for different reasons.
Closes #226
|