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.)
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?
With respect to tj3Transform(), this addresses an oversight from
bb1d540a807783a3db8b85bab2993d70b1330287.
Note to self: A convenience function/method for computing the worst-case
transformed JPEG size for a particular transform would be nice.
- When transforming, the worst-case JPEG buffer size depends on the
subsampling level used in the destination image, since a grayscale
transform might have been applied.
- Parentheses Police
Put all general functions at the top of the list, and ensure that all
functions are defined before they are mentioned. Also consistify the
function ordering between turbojpeg.h and turbojpeg.c
Lossless cropping is performed after other lossless transform
operations, so the cropping region must be specified relative to the
destination image dimensions and level of chrominance subsampling, not
the source image dimensions and level of chrominance subsampling.
More specifically, if the lossless transform operation swaps the X and Y
axes, or if the image is converted to grayscale, then that changes the
cropping region requirements.
The JPEG-1 spec never uses the term "MCU block". That term is rarely
used in other literature to describe the equivalent of an MCU in an
interleaved JPEG image, but the libjpeg documentation uses "iMCU" to
describe the same thing. "iMCU" is a better term, since the equivalent
of an interleaved MCU can contain multiple DCT blocks (or samples in
lossless mode) that are only grouped together if the image is
interleaved.
In the case of restart markers, "MCU block" was used in the libjpeg
documentation instead of "MCU", but "MCU" is more accurate and less
confusing. (The restart interval is literally in MCUs, where one MCU
is one data unit in a non-interleaved JPEG image and multiple data units
in a multi-component interleaved JPEG image.)
In the case of 9b704f96b2dccc54363ad7a2fe8e378fc1a2893b, the issue was
actually with progressive JPEG images exactly two DCT blocks wide, not
two MCU blocks wide.
This commit also defines "MCU" and "MCU row" in the description of the
various restart marker options/parameters. Although an MCU row is
technically always a row of samples in lossless mode, "sample row" was
confusing, since it is used in other places to describe a row of samples
for a single component (whereas an MCU row in a typical lossless JPEG
image consists of a row of interleaved samples for all components.)
TJ*PARAM_RESTARTBLOCKS technically works with lossless compression, but
it is not useful, since the value must be equal to the number of samples
in a row. (In other words, it is no different than
TJ*PARAM_RESTARTINROWS, except that it requires the user to do more
math.)
- "Optimized baseline entropy coding" = "Huffman table optimization"
"Optimized baseline entropy coding" was meant to emphasize that the
feature is only useful when generating baseline (single-scan lossy
8-bit-per-sample Huffman-coded) JPEG images, because it is
automatically enabled when generating Huffman-coded progressive
(multi-scan), 12-bit-per-sample, and lossless JPEG images. However,
Huffman table optimization isn't actually an integral part of those
non-baseline modes. You can forego Huffman table optimization with
12-bit data precision if you supply your own Huffman tables. The spec
doesn't require it with progressive or lossless mode, either, although
our implementation does. Furthermore, "baseline" describes more than
just the type of entropy coding used. It was incorrect to say that
optimized "baseline" entropy coding is automatically enabled for
Huffman-coded progressive, 12-bit-per-sample, and lossless JPEG
images, since those are clearly not baseline images.
- "Progressive entropy coding" = "Progressive JPEG"
"Progressive" describes more than just the type of entropy coding
used. (In fact, both Huffman-coded and arithmetic-coded images can be
progressive.)
- Mention that TJPARAM_OPTIMIZE/TJ.PARAM_OPTIMIZE can be used with
lossless transformation as well.
- General wordsmithing
- Formatting tweaks
Creating 12-bit-per-sample JPEG images from GIF input images was a
useful testing feature when the data precision was a compile-time
setting. However, now that the data precision is a runtime setting,
it doesn't make sense for cjpeg to allow data precisions other than
8-bit with GIF input images. GIF images are limited to 256 colors from
a palette of 8-bit-per-component RGB values, so they cannot take
advantage of the additional gamut afforded by higher data precisions.
- 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
- Clarify that lossless JPEG is slower than and doesn't compress as well
as lossy JPEG. (That should be obvious, because "lossy" literally
means that data is thrown away.)
- Re-generate TurboJPEG C API documentation using Doxygen 1.9.8.
- Clarify that setting the data_precision field in jpeg_compress_struct
to 16 requires lossless mode.
- Explain what the predictor selection value actually does. (Refer to
Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994, Section
H.1.2.1.)
TJPARAM_MAXPIXELS was previously hidden and used only for fuzz testing,
but it is potentially useful for calling applications as well,
particularly if they want to guard against excessive memory consumption
by the tj3LoadImage*() functions. The parameter has also been extended
to decompression and lossless transformation functions/methods, mainly
as a convenience. (It was already possible for calling applications to
impose their own JPEG image size limits by reading the JPEG header prior
to decompressing or transforming the image.)
This corresponds to max_memory_to_use in the jpeg_memory_mgr struct in
the libjpeg API, except that the TurboJPEG parameter is specified in
megabytes. Because this is 2023 and computers with less than 1 MB of
memory are not a thing (at least not within the scope of libjpeg-turbo
support), it isn't useful to allow a limit less than 1 MB to be
specified. Furthermore, because TurboJPEG parameters are signed
integers, if we allowed the memory limit to be specified in bytes, then
it would be impossible to specify a limit larger than 2 GB on 64-bit
machines. Because max_memory_to_use is a long signed integer,
effectively we can specify a limit of up to 2 petabytes on 64-bit
machines if the TurboJPEG parameter is specified in megabytes. (2 PB
should be enough for anybody, right?)
This commit also bumps the TurboJPEG API version to 3.0.1. Since the
TurboJPEG API version no longer tracks the libjpeg-turbo version, it
makes sense to increment the API revision number when adding constants,
to increment the minor version number when adding functions, and to
increment the major version number for a complete overhaul.
This commit also removes the vestigial TJ_NUMPARAM macro, which was
never defined because it proved unnecessary.
Partially implements #735
Referring to
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=60379
there are some specially-crafted malformed JPEG images that, when
transformed to grayscale, will exceed the worst-case transformed
grayscale JPEG image size. This is similar in nature to the issue fixed
by c8d52f1c4c7480277b91420c27b2548d4c8e9043, except that in this case,
the issue occurs regardless of the amount of metadata in the source
image. Also, the tj3Transform() function, the
Java_org_libjpegturbo_turbojpeg_TJTransformer_transform() JNI function,
and TJBench were behaving correctly in this case, because the TurboJPEG
API documentation specifies that the source image's subsampling type
should be used when computing the worst-case transformed JPEG image
size. (However, only the Java API documentation specified that. Oops.
The C API documentation now does as well.) The documented usage
mitigates the issue, and only the transform fuzzer did not adhere to
that. Thus, this was an issue with the fuzzer itself rather than an
issue with the library.
This allows losslessly transposed or rotated 4:1:1 JPEG images to be
losslessly cropped, partially decompressed, or decompressed to planar
YUV images.
Because tj3Transform() allows multiple lossless transformations to be
chained together, all subsampling options need to have a corresponding
transposed subsampling option. (This is why 4:4:0 was originally
implemented as well.) Otherwise, the documentation would be technically
incorrect. It says that images with unknown subsampling types cannot be
losslessly cropped, partially decompressed, or decompressed to planar
YUV images, but it doesn't say anything about images with known
subsampling types whose subsampling type becomes unknown if the image is
rotated or transposed. This is one of those situations in which it is
easier to implement a feature that works around the problem than to
document the problem.
Closes#659
This actually works and apparently always has worked. It only failed
because the libjpeg code, which did not originally support arithmetic
coding, assumed that optimize_coding should always be TRUE for 12-bit
data precision.
(ChangeLog update forthcoming)
- Prefix all function names with "tj3" and remove version suffixes from
function names. (Future API overhauls will increment the prefix to
"tj4", etc., thus retaining backward API/ABI compatibility without
versioning each individual function.)
- Replace stateless boolean flags (including TJ*FLAG_ARITHMETIC and
TJ*FLAG_LOSSLESS, which were never released) with stateful integer
parameters, the value of which persists between function calls.
* Use parameters for the JPEG quality and subsampling as well, in
order to eliminate the awkwardness of specifying function arguments
that weren't relevant for lossless compression.
* tj3DecompressHeader() now stores all relevant information about the
JPEG image, including the width, height, subsampling type, entropy
coding type, etc. in parameters rather than returning that
information in its arguments.
* TJ*FLAG_LIMITSCANS has been reimplemented as an integer parameter
(TJ*PARAM_SCANLIMIT) that allows the number of scans to be
specified.
- Use the const keyword for all pointer arguments to unmodified
buffers, as well as for both dimensions of 2D pointers. Addresses
#395.
- Use size_t rather than unsigned long to represent buffer sizes, since
unsigned long is a 32-bit type on Windows. Addresses #24.
- Return 0 from all buffer size functions if an error occurs, rather
than awkwardly trying to return -1 in an unsigned data type.
- Implement 12-bit and 16-bit data precision using dedicated
compression, decompression, and image I/O functions/methods.
* Suffix the names of all data-precision-specific functions with 8,
12, or 16.
* Because the YUV functions are intended to be used for video, they
are currently only implemented with 8-bit data precision, but they
can be expanded to 12-bit data precision in the future, if
necessary.
* Extend TJUnitTest and TJBench to test 12-bit and 16-bit data
precision, using a new -precision option.
* Add appropriate regression tests for all of the above to the 'test'
target.
* Extend tjbenchtest to test 12-bit and 16-bit data precision, and
add separate 'tjtest12' and 'tjtest16' targets.
* BufferedImage I/O in the Java API is currently limited to 8-bit
data precision, since the BufferedImage class does not
straightforwardly support higher data precisions.
* Extend the PPM reader to convert 12-bit and 16-bit PBMPLUS files
to grayscale or CMYK pixels, as it already does for 8-bit files.
- Properly accommodate lossless JPEG using dedicated parameters
(TJ*PARAM_LOSSLESS, TJ*PARAM_LOSSLESSPSV, and TJ*PARAM_LOSSLESSPT),
rather than using a flag and awkwardly repurposing the JPEG quality.
Update TJBench to properly reflect whether a JPEG image is lossless.
- Re-organize the TJBench usage screen.
- Update the Java docs using Java 11, to improve the formatting and
eliminate HTML frames.
- Use the accurate integer DCT algorithm by default for both
compression and decompression, since the "fast" algorithm is a legacy
feature, it does not pass the ISO compliance tests, and it is not
actually faster on modern x86 CPUs.
* Remove the -accuratedct option from TJBench and TJExample.
- Re-implement the 'tjtest' target using a CMake script that enables
the appropriate tests, depending on the data precision and whether or
not the Java API is part of the build.
- Consolidate the C and Java versions of tjbenchtest into one script.
- Consolidate the C and Java versions of tjexampletest into one script.
- Combine all initialization functions into a single function
(tj3Init()) that accepts an integer parameter specifying the
subsystems to initialize.
- Enable decompression scaling explicitly, using a new function/method
(tj3SetScalingFactor()/TJDecompressor.setScalingFactor()), rather
than implicitly using awkward "desired width"/"desired height"
parameters.
- Introduce a new macro/constant (TJUNSCALED/TJ.UNSCALED) that maps to
a scaling factor of 1/1.
- Implement partial image decompression, using a new function/method
(tj3SetCroppingRegion()/TJDecompressor.setCroppingRegion()) and
TJBench option (-crop). Extend tjbenchtest to test the new feature.
Addresses #1.
- Allow the JPEG colorspace to be specified explicitly when
compressing, using a new parameter (TJ*PARAM_COLORSPACE). This
allows JPEG images with the RGB and CMYK colorspaces to be created.
- Remove the error/difference image feature from TJBench. Identical
images to the ones that TJBench created can be generated using
ImageMagick with
'magick composite <original_image> <output_image> -compose difference <diff_image>'
- Handle JPEG images with unknown subsampling types. TJ*PARAM_SUBSAMP
is set to TJ*SAMP_UNKNOWN (== -1) for such images, but they can still
be decompressed fully into packed-pixel images or losslessly
transformed (with the exception of lossless cropping.) They cannot
be partially decompressed or decompressed into planar YUV images.
Note also that TJBench, due to its lack of support for imperfect
transforms, requires that the subsampling type be known when
rotating, flipping, or transversely transposing an image. Addresses
#436
- The Java version of TJBench now has identical functionality to the C
version. This was accomplished by (somewhat hackishly) calling the
TurboJPEG C image I/O functions through JNI and copying the pixels
between the C heap and the Java heap.
- Add parameters (TJ*PARAM_RESTARTROWS and TJ*PARAM_RESTARTBLOCKS) and
a TJBench option (-restart) to allow the restart marker interval to
be specified when compressing. Eliminate the undocumented TJ_RESTART
environment variable.
- Add a parameter (TJ*PARAM_OPTIMIZE), a transform option
(TJ*OPT_OPTIMIZE), and a TJBench option (-optimize) to allow
optimized baseline Huffman coding to be specified when compressing.
Eliminate the undocumented TJ_OPTIMIZE environment variable.
- Add parameters (TJ*PARAM_XDENSITY, TJ*PARAM_DENSITY, and
TJ*DENSITYUNITS) to allow the pixel density to be specified when
compressing or saving a Windows BMP image and to be queried when
decompressing or loading a Windows BMP image. Addresses #77.
- Refactor the fuzz targets to use the new API.
* Extend decompression coverage to 12-bit and 16-bit data precision.
* Replace the awkward cjpeg12 and cjpeg16 targets with proper
TurboJPEG-based compress12, compress12-lossless, and
compress16-lossless targets
- Fix innocuous UBSan warnings uncovered by the new fuzzers.
- Implement previous versions of the TurboJPEG API by wrapping the new
functions (tested by running the 2.1.x versions of TJBench, via
tjbenchtest, and TJUnitTest against the new implementation.)
* Remove all JNI functions for deprecated Java methods and implement
the deprecated methods using pure Java wrappers. It should be
understood that backward API compatibility in Java applies only to
the Java classes and that one cannot mix and match a JAR file from
one version of libjpeg-turbo with a JNI library from another
version.
- tj3Destroy() now silently accepts a NULL handle.
- tj3Alloc() and tj3Free() now return/accept void pointers, as malloc()
and free() do.
- The image I/O functions now accept a TurboJPEG instance handle, which
is used to transmit/receive parameters and to receive error
information.
Closes#517
- TJBench/TJUnitTest: Wordsmith command-line output
- Java: "decompress operations"="decompression operations"
- tjLoadImage(): Error message tweak
- Don't mention compression performance in the description of
TJXOPT_PROGRESSIVE/TJTransform.OPT_PROGRESSIVE, because the image has
already been compressed at that point.
(Oversights from 9a146f0f23b01869e1bf7c478e12b43f83d59c32)
- Wordsmithing, formatting, and grammar tweaks
- Various clarifications and corrections, including specifying whether
a particular buffer or image is used as a source or destination
- Accommodate/mention features that were introduced since the API
documentation was created.
- For clarity, use "packed-pixel" to describe uncompressed
source/destination images that are not planar YUV.
- Use "row" rather than "line" to refer to a single horizontal group of
pixels or component values, for consistency with the libjpeg API
documentation. (libjpeg also uses "scanline", which is a more archaic
term.)
- Use "alignment" rather than "padding" to refer to the number of bytes
by which a row's width is evenly divisible. This consistifies the
documention of the YUV functions and tjLoadImage(). ("Padding"
typically refers to the number of bytes added to each row, which is
not the same thing.)
- Remove all references to "the underlying codec." Although the
TurboJPEG API originated as a cross-platform wrapper for the Intel
Integrated Performance Primitives, Sun mediaLib, QuickTime, and
libjpeg, none of those TurboJPEG implementations has been maintained
since 2009. Nothing would prevent someone from implementing the
TurboJPEG API without libjpeg-turbo, but such an implementation would
not necessarily have an "underlying codec." (It could be fully
self-contained.)
- Use "destination image" rather than "output image", for consistency,
or describe the type of image that will be output.
- Avoid the term "image buffer" and instead use "byte buffer" to
refer to buffers that will hold JPEG images, or describe the type of
image that will be contained in the buffer. (The Java documentation
doesn't use "byte buffer", because the buffer arrays literally have
"byte" in front of them, and since Java doesn't have pointers, it is
not possible for mere mortals to store any other type of data in those
arrays.)
- C: Use "unified" to describe YUV images stored in a single buffer, for
consistency with the Java documentation.
- Use "planar YUV" rather than "YUV planar". Is is our convention to
describe images using {component layout} {colorspace/pixel format}
{image function}, e.g. "packed-pixel RGB source image" or "planar YUV
destination image."
- C: Document the TurboJPEG API version in which a particular function
or macro was introduced, and reorder the backward compatibility
function stubs in turbojpeg.h alphabetically by API version.
- C: Use Markdown rather than HTML tags, where possible, in the Doxygen
comments.
Because the PAD() macro can only handle powers of 2, this is a necessary
restriction (and a documented one, except in the case of
tjCompressFromYUV()-- oops.) Failing to check the 'pad' argument
caused tjBufSizeYUV2() to return bogus results if 'pad' was less than 1
or otherwise not a power of 2. tjEncodeYUV3() and tjDecodeYUV()
effectively treated a 'pad' value of 0 as unpadded, but that was subtle
and undocumented behavior. tjCompressFromYUV() did not check whether
'pad' was a power of 2, so the strides passed to
tjCompressFromYUVPlanes() would have been incorrect if 'pad' was not a
power of 2. That would not have caused tjCompressFromYUV() to overrun
the source buffer, as long as the calling application allocated the
buffer based on the return value of tjBufSizeYUV2() (which computes the
strides in the same manner as tjCompressFromYUV().) However, if the
calling application attempted to initialize the source buffer using
correctly-computed strides, then it could have overrun its own
buffer in certain cases or produced incorrect JPEG images in others.
Realistically, there is no reason why an application would want to pass
a non-power-of-2 'pad' value to a TurboJPEG API function, so this commit
is about user-proofing the API rather than fixing any known issue.
Add a new TurboJPEG C API function (tjDecompressHeader4()) and Java API
method (TJDecompressor.getFlags()) that return the bitwise OR of any
flags that are relevant to the JPEG image being decompressed (currently
TJFLAG_PROGRESSIVE, TJFLAG_ARITHMETIC, TJFLAG_LOSSLESS, and their Java
equivalents.) This allows a calling program to determine whether the
image being decompressed is a lossless JPEG image, which means that the
decompression scaling feature will not be available and that a
full-sized destination buffer should be allocated.
More specifically, this fixes a buffer overrun in TJBench, TJExample,
and the decompress* fuzz targets that occurred when attempting (in vain)
to decompress a lossless JPEG image with decompression scaling enabled.
+ document that tjFree() accepts NULL pointers without complaint.
Effectively, it has had that behavior all along, but the API does not
guarantee that tjFree() will be implemented with free() behind the
scenes, so it's best to formalize the behavior.
Loading RGB image files into a grayscale buffer isn't a particularly
useful feature, given that libjpeg-turbo can perform this conversion
much more optimally (with SIMD acceleration on some platforms) during
the compression process. Also, the RGB2GRAY() macro was not producing
deterministic cross-platform results because of variations in the
round-off behavior of various floating point implementations, so
`tjunittest -bmp` was failing in i386 builds.
