3.0.3
=====

### Significant changes relative to 3.0.2:

1. Fixed an issue in the build system, introduced in 3.0.2, that caused all
libjpeg-turbo components to depend on the Visual C++ run-time DLL when built
with Visual C++ and CMake 3.15 or later, regardless of value of the
`WITH_CRT_DLL` CMake variable.

2. The x86-64 SIMD extensions now include support for Intel Control-flow
Enforcement Technology (CET), which is enabled automatically if CET is enabled
in the C compiler.

3. Fixed a regression introduced by 3.0 beta2[6] that made it impossible for
calling applications to supply custom Huffman tables when generating
12-bit-per-component lossy JPEG images using the libjpeg API.

4. Fixed a segfault that occurred when attempting to use the jpegtran `-drop`
option with a specially-crafted malformed input image or drop image
(specifically an image in which all of the scans contain fewer components than
the number of components specified in the Start Of Frame segment.)


3.0.2
=====

### Significant changes relative to 3.0.1:

1. Fixed a signed integer overflow in the `tj3CompressFromYUV8()`,
`tj3DecodeYUV8()`, `tj3DecompressToYUV8()`, and `tj3EncodeYUV8()` functions,
detected by the Clang and GCC undefined behavior sanitizers, that could be
triggered by setting the `align` parameter to an unreasonably large value.
This issue did not pose a security threat, but removing the warning made it
easier to detect actual security issues, should they arise in the future.

2. Introduced a new parameter (`TJPARAM_MAXMEMORY` in the TurboJPEG C API and
`TJ.PARAM_MAXMEMORY` in the TurboJPEG Java API) and a corresponding TJBench
option (`-maxmemory`) for specifying the maximum amount of memory (in
megabytes) that will be allocated for intermediate buffers, which are used with
progressive JPEG compression and decompression, optimized baseline entropy
coding, lossless JPEG compression, and lossless transformation.  The new
parameter and option serve the same purpose as the `max_memory_to_use` field in
the `jpeg_memory_mgr` struct in the libjpeg API, the `JPEGMEM` environment
variable, and the cjpeg/djpeg/jpegtran `-maxmemory` option.

3. Introduced a new parameter (`TJPARAM_MAXPIXELS` in the TurboJPEG C API and
`TJ.PARAM_MAXPIXELS` in the TurboJPEG Java API) and a corresponding TJBench
option (`-maxpixels`) for specifying the maximum number of pixels that the
decompression, lossless transformation, and packed-pixel image loading
functions/methods will process.

4. Fixed an error ("Unsupported color conversion request") that occurred when
attempting to decompress a 3-component lossless JPEG image without an Adobe
APP14 marker.  The decompressor now assumes that a 3-component lossless JPEG
image without an Adobe APP14 marker uses the RGB colorspace if its component
IDs are 1, 2, and 3.


3.0.1
=====

### Significant changes relative to 3.0.0:

1. The x86-64 SIMD functions now use a standard stack frame, prologue, and
epilogue so that debuggers and profilers can reliably capture backtraces from
within the functions.

2. Fixed two minor issues in the interblock smoothing algorithm that caused
mathematical (but not necessarily perceptible) edge block errors when
decompressing progressive JPEG images exactly two MCU blocks in width or that
use vertical chrominance subsampling.

3. Fixed a regression introduced by 3.0 beta2[6] that, in rare cases, caused
the C Huffman encoder (which is not used by default on x86 and Arm CPUs) to
generate incorrect results if the Neon SIMD extensions were explicitly disabled
at build time (by setting the `WITH_SIMD` CMake variable to `0`) in an AArch64
build of libjpeg-turbo.


3.0.0
=====

### Significant changes relative to 3.0 beta2:

1. The TurboJPEG API now supports 4:4:1 (transposed 4:1:1) chrominance
subsampling, which allows losslessly transposed or rotated 4:1:1 JPEG images to
be losslessly cropped, partially decompressed, or decompressed to planar YUV
images.

2. Fixed various segfaults and buffer overruns (CVE-2023-2804) that occurred
when attempting to decompress various specially-crafted malformed
12-bit-per-component and 16-bit-per-component lossless JPEG images using color
quantization or merged chroma upsampling/color conversion.  The underlying
cause of these issues was that the color quantization and merged chroma
upsampling/color conversion algorithms were not designed with lossless
decompression in mind.  Since libjpeg-turbo explicitly does not support color
conversion when compressing or decompressing lossless JPEG images, merged
chroma upsampling/color conversion never should have been enabled for such
images.  Color quantization is a legacy feature that serves little or no
purpose with lossless JPEG images, so it is also now disabled when
decompressing such images.  (As a result, djpeg can no longer decompress a
lossless JPEG image into a GIF image.)

3. Fixed an oversight in 1.4 beta1[8] that caused various segfaults and buffer
overruns when attempting to decompress various specially-crafted malformed
12-bit-per-component JPEG images using djpeg with both color quantization and
RGB565 color conversion enabled.

4. Fixed an issue whereby `jpeg_crop_scanline()` sometimes miscalculated the
downsampled width for components with 4x2 or 2x4 subsampling factors if
decompression scaling was enabled.  This caused the components to be upsampled
incompletely, which caused the color converter to read from uninitialized
memory.  With 12-bit data precision, this caused a buffer overrun or underrun
and subsequent segfault if the sample value read from uninitialized memory was
outside of the valid sample range.

5. Fixed a long-standing issue whereby the `tj3Transform()` function, when used
with the `TJXOP_TRANSPOSE`, `TJXOP_TRANSVERSE`, `TJXOP_ROT90`, or
`TJXOP_ROT270` transform operation and without automatic JPEG destination
buffer (re)allocation or lossless cropping, computed the worst-case transformed
JPEG image size based on the source image dimensions rather than the
transformed image dimensions.  If a calling program allocated the JPEG
destination buffer based on the transformed image dimensions, as the API
documentation instructs, and attempted to transform a specially-crafted 4:2:2,
4:4:0, 4:1:1, or 4:4:1 JPEG source image containing a large amount of metadata,
the issue caused `tj3Transform()` to overflow the JPEG destination buffer
rather than fail gracefully.  The issue could be worked around by setting
`TJXOPT_COPYNONE`.  Note that, irrespective of this issue, `tj3Transform()`
cannot reliably transform JPEG source images that contain a large amount of
metadata unless automatic JPEG destination buffer (re)allocation is used or
`TJXOPT_COPYNONE` is set.

6. Fixed a regression introduced by 3.0 beta2[6] that prevented the djpeg
`-map` option from working when decompressing 12-bit-per-component lossy JPEG
images.

7. Fixed an issue that caused the C Huffman encoder (which is not used by
default on x86 and Arm CPUs) to read from uninitialized memory when attempting
to transform a specially-crafted malformed arithmetic-coded JPEG source image
into a baseline Huffman-coded JPEG destination image.


2.1.91 (3.0 beta2)
==================

### Significant changes relative to 2.1.5.1:

1. Significantly sped up the computation of optimal Huffman tables.  This
speeds up the compression of tiny images by as much as 2x and provides a
noticeable speedup for images as large as 256x256 when using optimal Huffman
tables.

2. All deprecated fields, constructors, and methods in the TurboJPEG Java API
have been removed.

3. Arithmetic entropy coding is now supported with 12-bit-per-component JPEG
images.

4. Overhauled the TurboJPEG API to address long-standing limitations and to
make the API more extensible and intuitive:

     - All C function names are now prefixed with `tj3`, and all version
suffixes have been removed from the function names.  Future API overhauls will
increment the prefix to `tj4`, etc., thus retaining backward API/ABI
compatibility without versioning each individual function.
     - Stateless boolean flags have been replaced with stateful integer API
parameters, the values of which persist between function calls.  New
functions/methods (`tj3Set()`/`TJCompressor.set()`/`TJDecompressor.set()` and
`tj3Get()`/`TJCompressor.get()`/`TJDecompressor.get()`) can be used to set and
query the value of a particular API parameter.
     - The JPEG quality and subsampling are now implemented using API
parameters rather than stateless function arguments (C) or dedicated set/get
methods (Java.)
     - `tj3DecompressHeader()` now stores all relevant information about the
JPEG image, including the width, height, subsampling type, entropy coding
algorithm, etc., in API parameters rather than returning that information
through pointer arguments.
     - `TJFLAG_LIMITSCANS`/`TJ.FLAG_LIMITSCANS` has been reimplemented as an
API parameter (`TJPARAM_SCANLIMIT`/`TJ.PARAM_SCANLIMIT`) that allows the number
of scans to be specified.
     - Optimized baseline entropy coding (the computation of optimal Huffman
tables, as opposed to using the default Huffman tables) can now be specified,
using a new API parameter (`TJPARAM_OPTIMIZE`/`TJ.PARAM_OPTIMIZE`), a new
transform option (`TJXOPT_OPTIMIZE`/`TJTransform.OPT_OPTIMIZE`), and a new
TJBench option (`-optimize`.)
     - Arithmetic entropy coding can now be specified or queried, using a new
API parameter (`TJPARAM_ARITHMETIC`/`TJ.PARAM_ARITHMETIC`), a new transform
option (`TJXOPT_ARITHMETIC`/`TJTransform.OPT_ARITHMETIC`), and a new TJBench
option (`-arithmetic`.)
     - The restart marker interval can now be specified, using new API
parameters (`TJPARAM_RESTARTROWS`/`TJ.PARAM_RESTARTROWS` and
`TJPARAM_RESTARTBLOCKS`/`TJ.PARAM_RESTARTBLOCKS`) and a new TJBench option
(`-restart`.)
     - Pixel density can now be specified or queried, using new API parameters
(`TJPARAM_XDENSITY`/`TJ.PARAM_XDENSITY`,
`TJPARAM_YDENSITY`/`TJ.PARAM_YDENSITY`, and
`TJPARAM_DENSITYUNITS`/`TJ.PARAM_DENSITYUNITS`.)
     - The accurate DCT/IDCT algorithms are now the default for both
compression and decompression, since the "fast" algorithms are considered to be
a legacy feature.  (The "fast" algorithms do not pass the ISO compliance tests,
and those algorithms are not any faster than the accurate algorithms on modern
x86 CPUs.)
     - All C initialization functions have been combined into a single function
(`tj3Init()`) that accepts an integer argument specifying the subsystems to
initialize.
     - All C functions now use the `const` keyword for pointer arguments that
point to unmodified buffers (and for both dimensions of pointer arguments that
point to sets of unmodified buffers.)
     - All C functions now use `size_t` rather than `unsigned long` to
represent buffer sizes, for compatibility with `malloc()` and to avoid
disparities in the size of `unsigned long` between LP64 (Un*x) and LLP64
(Windows) operating systems.
     - All C buffer size functions now return 0 if an error occurs, rather than
trying to awkwardly return -1 in an unsigned data type (which could easily be
misinterpreted as a very large value.)
     - Decompression scaling is now enabled explicitly, using a new
function/method (`tj3SetScalingFactor()`/`TJDecompressor.setScalingFactor()`),
rather than implicitly using awkward "desired width"/"desired height"
arguments.
     - Partial image decompression has been implemented, using a new
function/method (`tj3SetCroppingRegion()`/`TJDecompressor.setCroppingRegion()`)
and a new TJBench option (`-crop`.)
     - The JPEG colorspace can now be specified explicitly when compressing,
using a new API parameter (`TJPARAM_COLORSPACE`/`TJ.PARAM_COLORSPACE`.)  This
allows JPEG images with the RGB and CMYK colorspaces to be created.
     - TJBench no longer generates error/difference images, since identical
functionality is already available in ImageMagick.
     - JPEG images with unknown subsampling configurations can now be
fully decompressed into packed-pixel images or losslessly transformed (with the
exception of lossless cropping.)  They cannot currently be partially
decompressed or decompressed into planar YUV images.
     - `tj3Destroy()` now silently accepts a NULL handle.
     - `tj3Alloc()` and `tj3Free()` now return/accept void pointers, as
`malloc()` and `free()` do.
     - The C image I/O functions now accept a TurboJPEG instance handle, which
is used to transmit/receive API parameter values and to receive error
information.

5. Added support for 8-bit-per-component, 12-bit-per-component, and
16-bit-per-component lossless JPEG images.  A new libjpeg API function
(`jpeg_enable_lossless()`), TurboJPEG API parameters
(`TJPARAM_LOSSLESS`/`TJ.PARAM_LOSSLESS`,
`TJPARAM_LOSSLESSPSV`/`TJ.PARAM_LOSSLESSPSV`, and
`TJPARAM_LOSSLESSPT`/`TJ.PARAM_LOSSLESSPT`), and a cjpeg/TJBench option
(`-lossless`) can be used to create a lossless JPEG image.  (Decompression of
lossless JPEG images is handled automatically.)  Refer to
[libjpeg.txt](libjpeg.txt), [usage.txt](usage.txt), and the TurboJPEG API
documentation for more details.

6. Added support for 12-bit-per-component (lossy and lossless) and
16-bit-per-component (lossless) JPEG images to the libjpeg and TurboJPEG APIs:

     - The existing `data_precision` field in `jpeg_compress_struct` and
`jpeg_decompress_struct` has been repurposed to enable the creation of
12-bit-per-component and 16-bit-per-component JPEG images or to detect whether
a 12-bit-per-component or 16-bit-per-component JPEG image is being
decompressed.
     - New 12-bit-per-component and 16-bit-per-component versions of
`jpeg_write_scanlines()` and `jpeg_read_scanlines()`, as well as new
12-bit-per-component versions of `jpeg_write_raw_data()`,
`jpeg_skip_scanlines()`, `jpeg_crop_scanline()`, and `jpeg_read_raw_data()`,
provide interfaces for compressing from/decompressing to 12-bit-per-component
and 16-bit-per-component packed-pixel and planar YUV image buffers.
     - New 12-bit-per-component and 16-bit-per-component compression,
decompression, and image I/O functions/methods have been added to the TurboJPEG
API, and a new API parameter (`TJPARAM_PRECISION`/`TJ.PARAM_PRECISION`) can be
used to query the data precision of a JPEG image.  (YUV functions are currently
limited to 8-bit data precision but can be expanded to accommodate 12-bit data
precision in the future, if such is deemed beneficial.)
     - A new cjpeg and TJBench command-line argument (`-precision`) can be used
to create a 12-bit-per-component or 16-bit-per-component JPEG image.
(Decompression and transformation of 12-bit-per-component and
16-bit-per-component JPEG images is handled automatically.)

    Refer to [libjpeg.txt](libjpeg.txt), [usage.txt](usage.txt), and the
TurboJPEG API documentation for more details.


2.1.5.1
=======

### Significant changes relative to 2.1.5:

1. The SIMD dispatchers in libjpeg-turbo 2.1.4 and prior stored the list of
supported SIMD instruction sets in a global variable, which caused an innocuous
race condition whereby the variable could have been initialized multiple times
if `jpeg_start_*compress()` was called simultaneously in multiple threads.
libjpeg-turbo 2.1.5 included an undocumented attempt to fix this race condition
by making the SIMD support variable thread-local.  However, that caused another
issue whereby, if `jpeg_start_*compress()` was called in one thread and
`jpeg_read_*()` or `jpeg_write_*()` was called in a second thread, the SIMD
support variable was never initialized in the second thread.  On x86 systems,
this led the second thread to incorrectly assume that AVX2 instructions were
always available, and when it attempted to use those instructions on older x86
CPUs that do not support them, an illegal instruction error occurred.  The SIMD
dispatchers now ensure that the SIMD support variable is initialized before
dispatching based on its value.


2.1.5
=====

### Significant changes relative to 2.1.4:

1. Fixed issues in the build system whereby, when using the Ninja Multi-Config
CMake generator, a static build of libjpeg-turbo (a build in which
`ENABLE_SHARED` is `0`) could not be installed, a Windows installer could not
be built, and the Java regression tests failed.

2. Fixed a regression introduced by 2.0 beta1[15] that caused a buffer overrun
in the progressive Huffman encoder when attempting to transform a
specially-crafted malformed 12-bit-per-component JPEG image into a progressive
12-bit-per-component JPEG image using a 12-bit-per-component build of
libjpeg-turbo (`-DWITH_12BIT=1`.)  Given that the buffer overrun was fully
contained within the progressive Huffman encoder structure and did not cause a
segfault or other user-visible errant behavior, given that the lossless
transformer (unlike the decompressor) is not generally exposed to arbitrary
data exploits, and given that 12-bit-per-component builds of libjpeg-turbo are
uncommon, this issue did not likely pose a security risk.

3. Fixed an issue whereby, when using a 12-bit-per-component build of
libjpeg-turbo (`-DWITH_12BIT=1`), passing samples with values greater than 4095
or less than 0 to `jpeg_write_scanlines()` caused a buffer overrun or underrun
in the RGB-to-YCbCr color converter.

4. Fixed a floating point exception that occurred when attempting to use the
jpegtran `-drop` and `-trim` options to losslessly transform a
specially-crafted malformed JPEG image.

5. Fixed an issue in `tjBufSizeYUV2()` whereby it returned a bogus result,
rather than throwing an error, if the `align` parameter was not a power of 2.
Fixed a similar issue in `tjCompressFromYUV()` whereby it generated a corrupt
JPEG image in certain cases, rather than throwing an error, if the `align`
parameter was not a power of 2.

6. Fixed an issue whereby `tjDecompressToYUV2()`, which is a wrapper for
`tjDecompressToYUVPlanes()`, used the desired YUV image dimensions rather than
the actual scaled image dimensions when computing the plane pointers and
strides to pass to `tjDecompressToYUVPlanes()`.  This caused a buffer overrun
and subsequent segfault if the desired image dimensions exceeded the scaled
image dimensions.

7. Fixed an issue whereby, when decompressing a 12-bit-per-component JPEG image
(`-DWITH_12BIT=1`) using an alpha-enabled output color space such as
`JCS_EXT_RGBA`, the alpha channel was set to 255 rather than 4095.

8. Fixed an issue whereby the Java version of TJBench did not accept a range of
quality values.

9. Fixed an issue whereby, when `-progressive` was passed to TJBench, the JPEG
input image was not transformed into a progressive JPEG image prior to
decompression.


2.1.4
=====

### Significant changes relative to 2.1.3:

1. Fixed a regression introduced in 2.1.3 that caused build failures with
Visual Studio 2010.

2. The `tjDecompressHeader3()` function in the TurboJPEG C API and the
`TJDecompressor.setSourceImage()` method in the TurboJPEG Java API now accept
"abbreviated table specification" (AKA "tables-only") datastreams, which can be
used to prime the decompressor with quantization and Huffman tables that can be
used when decompressing subsequent "abbreviated image" datastreams.

3. libjpeg-turbo now performs run-time detection of AltiVec instructions on
OS X/PowerPC systems if AltiVec instructions are not enabled at compile time.
This allows both AltiVec-equipped (PowerPC G4 and G5) and non-AltiVec-equipped
(PowerPC G3) CPUs to be supported using the same build of libjpeg-turbo.

4. Fixed an error ("Bogus virtual array access") that occurred when attempting
to decompress a progressive JPEG image with a height less than or equal to one
iMCU (8 * the vertical sampling factor) using buffered-image mode with
interblock smoothing enabled.  This was a regression introduced by
2.1 beta1[6(b)].

5. Fixed two issues that prevented partial image decompression from working
properly with buffered-image mode:

     - Attempting to call `jpeg_crop_scanline()` after
`jpeg_start_decompress()` but before `jpeg_start_output()` resulted in an error
("Improper call to JPEG library in state 207".)
     - Attempting to use `jpeg_skip_scanlines()` resulted in an error ("Bogus
virtual array access") under certain circumstances.


2.1.3
=====

### Significant changes relative to 2.1.2:

1. Fixed a regression introduced by 2.0 beta1[7] whereby cjpeg compressed PGM
input files into full-color JPEG images unless the `-grayscale` option was
used.

2. cjpeg now automatically compresses GIF and 8-bit BMP input files into
grayscale JPEG images if the input files contain only shades of gray.

3. The build system now enables the intrinsics implementation of the AArch64
(Arm 64-bit) Neon SIMD extensions by default when using GCC 12 or later.

4. Fixed a segfault that occurred while decompressing a 4:2:0 JPEG image using
the merged (non-fancy) upsampling algorithms (that is, with
`cinfo.do_fancy_upsampling` set to `FALSE`) along with `jpeg_crop_scanline()`.
Specifically, the segfault occurred if the number of bytes remaining in the
output buffer was less than the number of bytes required to represent one
uncropped scanline of the output image.  For that reason, the issue could only
be reproduced using the libjpeg API, not using djpeg.


2.1.2
=====

### Significant changes relative to 2.1.1:

1. Fixed a regression introduced by 2.1 beta1[13] that caused the remaining
GAS implementations of AArch64 (Arm 64-bit) Neon SIMD functions (which are used
by default with GCC for performance reasons) to be placed in the `.rodata`
section rather than in the `.text` section.  This caused the GNU linker to
automatically place the `.rodata` section in an executable segment, which
prevented libjpeg-turbo from working properly with other linkers and also
represented a potential security risk.

2. Fixed an issue whereby the `tjTransform()` function incorrectly computed the
MCU block size for 4:4:4 JPEG images with non-unary sampling factors and thus
unduly rejected some cropping regions, even though those regions aligned with
8x8 MCU block boundaries.

3. Fixed a regression introduced by 2.1 beta1[13] that caused the build system
to enable the Arm Neon SIMD extensions when targetting Armv6 and other legacy
architectures that do not support Neon instructions.

4. libjpeg-turbo now performs run-time detection of AltiVec instructions on
FreeBSD/PowerPC systems if AltiVec instructions are not enabled at compile
time.  This allows both AltiVec-equipped and non-AltiVec-equipped CPUs to be
supported using the same build of libjpeg-turbo.

5. cjpeg now accepts a `-strict` argument similar to that of djpeg and
jpegtran, which causes the compressor to abort if an LZW-compressed GIF input
image contains incomplete or corrupt image data.


2.1.1
=====

### Significant changes relative to 2.1.0:

1. Fixed a regression introduced in 2.1.0 that caused build failures with
non-GCC-compatible compilers for Un*x/Arm platforms.

2. Fixed a regression introduced by 2.1 beta1[13] that prevented the Arm 32-bit
(AArch32) Neon SIMD extensions from building unless the C compiler flags
included `-mfloat-abi=softfp` or `-mfloat-abi=hard`.

3. Fixed an issue in the AArch32 Neon SIMD Huffman encoder whereby reliance on
undefined C compiler behavior led to crashes ("SIGBUS: illegal alignment") on
Android systems when running AArch32/Thumb builds of libjpeg-turbo built with
recent versions of Clang.

4. Added a command-line argument (`-copy icc`) to jpegtran that causes it to
copy only the ICC profile markers from the source file and discard any other
metadata.

5. libjpeg-turbo should now build and run on CHERI-enabled architectures, which
use capability pointers that are larger than the size of `size_t`.

6. Fixed a regression (CVE-2021-37972) introduced by 2.1 beta1[5] that caused a
segfault in the 64-bit SSE2 Huffman encoder when attempting to losslessly
transform a specially-crafted malformed JPEG image.


2.1.0
=====

### Significant changes relative to 2.1 beta1:

1. Fixed a regression (CVE-2021-29390) introduced by 2.1 beta1[6(b)] whereby
attempting to decompress certain progressive JPEG images with one or more
component planes of width 8 or less caused a buffer overrun.

2. Fixed a regression introduced by 2.1 beta1[6(b)] whereby attempting to
decompress a specially-crafted malformed progressive JPEG image caused the
block smoothing algorithm to read from uninitialized memory.

3. Fixed an issue in the Arm Neon SIMD Huffman encoders that caused the
encoders to generate incorrect results when using the Clang compiler with
Visual Studio.

4. Fixed a floating point exception (CVE-2021-20205) that occurred when
attempting to compress a specially-crafted malformed GIF image with a specified
image width of 0 using cjpeg.

5. Fixed a regression introduced by 2.0 beta1[15] whereby attempting to
generate a progressive JPEG image on an SSE2-capable CPU using a scan script
containing one or more scans with lengths divisible by 32 and non-zero
successive approximation low bit positions would, under certain circumstances,
result in an error ("Missing Huffman code table entry") and an invalid JPEG
image.

6. Introduced a new flag (`TJFLAG_LIMITSCANS` in the TurboJPEG C API and
`TJ.FLAG_LIMIT_SCANS` in the TurboJPEG Java API) and a corresponding TJBench
command-line argument (`-limitscans`) that causes the TurboJPEG decompression
and transform functions/operations to return/throw an error if a progressive
JPEG image contains an unreasonably large number of scans.  This allows
applications that use the TurboJPEG API to guard against an exploit of the
progressive JPEG format described in the report
["Two Issues with the JPEG Standard"](https://libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf).

7. The PPM reader now throws an error, rather than segfaulting (due to a buffer
overrun, CVE-2021-46822) or generating incorrect pixels, if an application
attempts to use the `tjLoadImage()` function to load a 16-bit binary PPM file
(a binary PPM file with a maximum value greater than 255) into a grayscale
image buffer or to load a 16-bit binary PGM file into an RGB image buffer.

8. Fixed an issue in the PPM reader that caused incorrect pixels to be
generated when using the `tjLoadImage()` function to load a 16-bit binary PPM
file into an extended RGB image buffer.

9. Fixed an issue whereby, if a JPEG buffer was automatically re-allocated by
one of the TurboJPEG compression or transform functions and an error
subsequently occurred during compression or transformation, the JPEG buffer
pointer passed by the application was not updated when the function returned.


2.0.90 (2.1 beta1)
==================

### Significant changes relative to 2.0.6:

1. The build system, x86-64 SIMD extensions, and accelerated Huffman codec now
support the x32 ABI on Linux, which allows for using x86-64 instructions with
32-bit pointers.  The x32 ABI is generally enabled by adding `-mx32` to the
compiler flags.

     Caveats:
     - CMake 3.9.0 or later is required in order for the build system to
automatically detect an x32 build.
     - Java does not support the x32 ABI, and thus the TurboJPEG Java API will
automatically be disabled with x32 builds.

2. Added Loongson MMI SIMD implementations of the RGB-to-grayscale, 4:2:2 fancy
chroma upsampling, 4:2:2 and 4:2:0 merged chroma upsampling/color conversion,
and fast integer DCT/IDCT algorithms.  Relative to libjpeg-turbo 2.0.x, this
speeds up:

     - the compression of RGB source images into grayscale JPEG images by
approximately 20%
     - the decompression of 4:2:2 JPEG images by approximately 40-60% when
using fancy upsampling
     - the decompression of 4:2:2 and 4:2:0 JPEG images by approximately
15-20% when using merged upsampling
     - the compression of RGB source images by approximately 30-45% when using
the fast integer DCT
     - the decompression of JPEG images into RGB destination images by
approximately 2x when using the fast integer IDCT

    The overall decompression speedup for RGB images is now approximately
2.3-3.7x (compared to 2-3.5x with libjpeg-turbo 2.0.x.)

3. 32-bit (Armv7 or Armv7s) iOS builds of libjpeg-turbo are no longer
supported, and the libjpeg-turbo build system can no longer be used to package
such builds.  32-bit iOS apps cannot run in iOS 11 and later, and the App Store
no longer allows them.

4. 32-bit (i386) OS X/macOS builds of libjpeg-turbo are no longer supported,
and the libjpeg-turbo build system can no longer be used to package such
builds.  32-bit Mac applications cannot run in macOS 10.15 "Catalina" and
later, and the App Store no longer allows them.

5. The SSE2 (x86 SIMD) and C Huffman encoding algorithms have been
significantly optimized, resulting in a measured average overall compression
speedup of 12-28% for 64-bit code and 22-52% for 32-bit code on various Intel
and AMD CPUs, as well as a measured average overall compression speedup of
0-23% on platforms that do not have a SIMD-accelerated Huffman encoding
implementation.

6. The block smoothing algorithm that is applied by default when decompressing
progressive Huffman-encoded JPEG images has been improved in the following
ways:

     - The algorithm is now more fault-tolerant.  Previously, if a particular
scan was incomplete, then the smoothing parameters for the incomplete scan
would be applied to the entire output image, including the parts of the image
that were generated by the prior (complete) scan.  Visually, this had the
effect of removing block smoothing from lower-frequency scans if they were
followed by an incomplete higher-frequency scan.  libjpeg-turbo now applies
block smoothing parameters to each iMCU row based on which scan generated the
pixels in that row, rather than always using the block smoothing parameters for
the most recent scan.
     - When applying block smoothing to DC scans, a Gaussian-like kernel with a
5x5 window is used to reduce the "blocky" appearance.

7. Added SIMD acceleration for progressive Huffman encoding on Arm platforms.
This speeds up the compression of full-color progressive JPEGs by about 30-40%
on average (relative to libjpeg-turbo 2.0.x) when using modern Arm CPUs.

8. Added configure-time and run-time auto-detection of Loongson MMI SIMD
instructions, so that the Loongson MMI SIMD extensions can be included in any
MIPS64 libjpeg-turbo build.

9. Added fault tolerance features to djpeg and jpegtran, mainly to demonstrate
methods by which applications can guard against the exploits of the JPEG format
described in the report
["Two Issues with the JPEG Standard"](https://libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf).

     - Both programs now accept a `-maxscans` argument, which can be used to
limit the number of allowable scans in the input file.
     - Both programs now accept a `-strict` argument, which can be used to
treat all warnings as fatal.

10. CMake package config files are now included for both the libjpeg and
TurboJPEG API libraries.  This facilitates using libjpeg-turbo with CMake's
`find_package()` function.  For example:

        find_package(libjpeg-turbo CONFIG REQUIRED)

        add_executable(libjpeg_program libjpeg_program.c)
        target_link_libraries(libjpeg_program PUBLIC libjpeg-turbo::jpeg)

        add_executable(libjpeg_program_static libjpeg_program.c)
        target_link_libraries(libjpeg_program_static PUBLIC
          libjpeg-turbo::jpeg-static)

        add_executable(turbojpeg_program turbojpeg_program.c)
        target_link_libraries(turbojpeg_program PUBLIC
          libjpeg-turbo::turbojpeg)

        add_executable(turbojpeg_program_static turbojpeg_program.c)
        target_link_libraries(turbojpeg_program_static PUBLIC
          libjpeg-turbo::turbojpeg-static)

11. Since the Unisys LZW patent has long expired, cjpeg and djpeg can now
read/write both LZW-compressed and uncompressed GIF files (feature ported from
jpeg-6a and jpeg-9d.)

12. jpegtran now includes the `-wipe` and `-drop` options from jpeg-9a and
jpeg-9d, as well as the ability to expand the image size using the `-crop`
option.  Refer to jpegtran.1 or usage.txt for more details.

13. Added a complete intrinsics implementation of the Arm Neon SIMD extensions,
thus providing SIMD acceleration on Arm platforms for all of the algorithms
that are SIMD-accelerated on x86 platforms.  This new implementation is
significantly faster in some cases than the old GAS implementation--
depending on the algorithms used, the type of CPU core, and the compiler.  GCC,
as of this writing, does not provide a full or optimal set of Neon intrinsics,
so for performance reasons, the default when building libjpeg-turbo with GCC is
to continue using the GAS implementation of the following algorithms:

     - 32-bit RGB-to-YCbCr color conversion
     - 32-bit fast and accurate inverse DCT
     - 64-bit RGB-to-YCbCr and YCbCr-to-RGB color conversion
     - 64-bit accurate forward and inverse DCT
     - 64-bit Huffman encoding

    A new CMake variable (`NEON_INTRINSICS`) can be used to override this
default.

    Since the new intrinsics implementation includes SIMD acceleration
for merged upsampling/color conversion, 1.5.1[5] is no longer necessary and has
been reverted.

14. The Arm Neon SIMD extensions can now be built using Visual Studio.

15. The build system can now be used to generate a universal x86-64 + Armv8
libjpeg-turbo SDK package for both iOS and macOS.


2.0.6
=====

### Significant changes relative to 2.0.5:

1. Fixed "using JNI after critical get" errors that occurred on Android
platforms when using any of the YUV encoding/compression/decompression/decoding
methods in the TurboJPEG Java API.

2. Fixed or worked around multiple issues with `jpeg_skip_scanlines()`:

     - Fixed segfaults (CVE-2020-35538) or "Corrupt JPEG data: premature end of
data segment" errors in `jpeg_skip_scanlines()` that occurred when
decompressing 4:2:2 or 4:2:0 JPEG images using merged (non-fancy)
upsampling/color conversion (that is, when setting `cinfo.do_fancy_upsampling`
to `FALSE`.)  2.0.0[6] was a similar fix, but it did not cover all cases.
     - `jpeg_skip_scanlines()` now throws an error if two-pass color
quantization is enabled.  Two-pass color quantization never worked properly
with `jpeg_skip_scanlines()`, and the issues could not readily be fixed.
     - Fixed an issue whereby `jpeg_skip_scanlines()` always returned 0 when
skipping past the end of an image.

3. The Arm 64-bit (Armv8) Neon SIMD extensions can now be built using MinGW
toolchains targetting Arm64 (AArch64) Windows binaries.

4. Fixed unexpected visual artifacts that occurred when using
`jpeg_crop_scanline()` and interblock smoothing while decompressing only the DC
scan of a progressive JPEG image.

5. Fixed an issue whereby libjpeg-turbo would not build if 12-bit-per-component
JPEG support (`WITH_12BIT`) was enabled along with libjpeg v7 or libjpeg v8
API/ABI emulation (`WITH_JPEG7` or `WITH_JPEG8`.)


2.0.5
=====

### Significant changes relative to 2.0.4:

1. Worked around issues in the MIPS DSPr2 SIMD extensions that caused failures
in the libjpeg-turbo regression tests.  Specifically, the
`jsimd_h2v1_downsample_dspr2()` and `jsimd_h2v2_downsample_dspr2()` functions
in the MIPS DSPr2 SIMD extensions are now disabled until/unless they can be
fixed, and other functions that are incompatible with big endian MIPS CPUs are
disabled when building libjpeg-turbo for such CPUs.

2. Fixed an oversight in the `TJCompressor.compress(int)` method in the
TurboJPEG Java API that caused an error ("java.lang.IllegalStateException: No
source image is associated with this instance") when attempting to use that
method to compress a YUV image.

3. Fixed an issue (CVE-2020-13790) in the PPM reader that caused a buffer
overrun in cjpeg, TJBench, or the `tjLoadImage()` function if one of the values
in a binary PPM/PGM input file exceeded the maximum value defined in the file's
header and that maximum value was less than 255.  libjpeg-turbo 1.5.0 already
included a similar fix for binary PPM/PGM files with maximum values greater
than 255.

4. The TurboJPEG API library's global error handler, which is used in functions
such as `tjBufSize()` and `tjLoadImage()` that do not require a TurboJPEG
instance handle, is now thread-safe on platforms that support thread-local
storage.


2.0.4
=====

### Significant changes relative to 2.0.3:

1. Fixed a regression in the Windows packaging system (introduced by
2.0 beta1[2]) whereby, if both the 64-bit libjpeg-turbo SDK for GCC and the
64-bit libjpeg-turbo SDK for Visual C++ were installed on the same system, only
one of them could be uninstalled.

2. Fixed a signed integer overflow and subsequent segfault that occurred when
attempting to decompress images with more than 715827882 pixels using the
64-bit C version of TJBench.

3. Fixed out-of-bounds write in `tjDecompressToYUV2()` and
`tjDecompressToYUVPlanes()` (sometimes manifesting as a double free) that
occurred when attempting to decompress grayscale JPEG images that were
compressed with a sampling factor other than 1 (for instance, with
`cjpeg -grayscale -sample 2x2`).

4. Fixed a regression introduced by 2.0.2[5] that caused the TurboJPEG API to
incorrectly identify some JPEG images with unusual sampling factors as 4:4:4
JPEG images.  This was known to cause a buffer overflow when attempting to
decompress some such images using `tjDecompressToYUV2()` or
`tjDecompressToYUVPlanes()`.

5. Fixed an issue (CVE-2020-17541), detected by ASan, whereby attempting to
losslessly transform a specially-crafted malformed JPEG image containing an
extremely-high-frequency coefficient block (junk image data that could never be
generated by a legitimate JPEG compressor) could cause the Huffman encoder's
local buffer to be overrun. (Refer to 1.4.0[9] and 1.4beta1[15].)  Given that
the buffer overrun was fully contained within the stack and did not cause a
segfault or other user-visible errant behavior, and given that the lossless
transformer (unlike the decompressor) is not generally exposed to arbitrary
data exploits, this issue did not likely pose a security risk.

6. The Arm 64-bit (Armv8) Neon SIMD assembly code now stores constants in a
separate read-only data section rather than in the text section, to support
execute-only memory layouts.


2.0.3
=====

### Significant changes relative to 2.0.2:

1. Fixed "using JNI after critical get" errors that occurred on Android
platforms when passing invalid arguments to certain methods in the TurboJPEG
Java API.

2. Fixed a regression in the SIMD feature detection code, introduced by
the AVX2 SIMD extensions (2.0 beta1[1]), that was known to cause an illegal
instruction exception, in rare cases, on CPUs that lack support for CPUID leaf
07H (or on which the maximum CPUID leaf has been limited by way of a BIOS
setting.)

3. The 4:4:0 (h1v2) fancy (smooth) chroma upsampling algorithm in the
decompressor now uses a similar bias pattern to that of the 4:2:2 (h2v1) fancy
chroma upsampling algorithm, rounding up or down the upsampled result for
alternate pixels rather than always rounding down.  This ensures that,
regardless of whether a 4:2:2 JPEG image is rotated or transposed prior to
decompression (in the frequency domain) or after decompression (in the spatial
domain), the final image will be similar.

4. Fixed an integer overflow and subsequent segfault that occurred when
attempting to compress or decompress images with more than 1 billion pixels
using the TurboJPEG API.

5. Fixed a regression introduced by 2.0 beta1[15] whereby attempting to
generate a progressive JPEG image on an SSE2-capable CPU using a scan script
containing one or more scans with lengths divisible by 16 would result in an
error ("Missing Huffman code table entry") and an invalid JPEG image.

6. Fixed an issue whereby `tjDecodeYUV()` and `tjDecodeYUVPlanes()` would throw
an error ("Invalid progressive parameters") or a warning ("Inconsistent
progression sequence") if passed a TurboJPEG instance that was previously used
to decompress a progressive JPEG image.


2.0.2
=====

### Significant changes relative to 2.0.1:

1. Fixed a regression introduced by 2.0.1[5] that prevented a runtime search
path (rpath) from being embedded in the libjpeg-turbo shared libraries and
executables for macOS and iOS.  This caused a fatal error of the form
"dyld: Library not loaded" when attempting to use one of the executables,
unless `DYLD_LIBRARY_PATH` was explicitly set to the location of the
libjpeg-turbo shared libraries.

2. Fixed an integer overflow and subsequent segfault (CVE-2018-20330) that
occurred when attempting to load a BMP file with more than 1 billion pixels
using the `tjLoadImage()` function.

3. Fixed a buffer overrun (CVE-2018-19664) that occurred when attempting to
decompress a specially-crafted malformed JPEG image to a 256-color BMP using
djpeg.

4. Fixed a floating point exception that occurred when attempting to
decompress a specially-crafted malformed JPEG image with a specified image
width or height of 0 using the C version of TJBench.

5. The TurboJPEG API will now decompress 4:4:4 JPEG images with 2x1, 1x2, 3x1,
or 1x3 luminance and chrominance sampling factors.  This is a non-standard way
of specifying 1x subsampling (normally 4:4:4 JPEGs have 1x1 luminance and
chrominance sampling factors), but the JPEG format and the libjpeg API both
allow it.

6. Fixed a regression introduced by 2.0 beta1[7] that caused djpeg to generate
incorrect PPM images when used with the `-colors` option.

7. Fixed an issue whereby a static build of libjpeg-turbo (a build in which
`ENABLE_SHARED` is `0`) could not be installed using the Visual Studio IDE.

8. Fixed a severe performance issue in the Loongson MMI SIMD extensions that
occurred when compressing RGB images whose image rows were not 64-bit-aligned.


2.0.1
=====

### Significant changes relative to 2.0.0:

1. Fixed a regression introduced with the new CMake-based Un*x build system,
whereby jconfig.h could cause compiler warnings of the form
`"HAVE_*_H" redefined` if it was included by downstream Autotools-based
projects that used `AC_CHECK_HEADERS()` to check for the existence of locale.h,
stddef.h, or stdlib.h.

2. The `jsimd_quantize_float_dspr2()` and `jsimd_convsamp_float_dspr2()`
functions in the MIPS DSPr2 SIMD extensions are now disabled at compile time
if the soft float ABI is enabled.  Those functions use instructions that are
incompatible with the soft float ABI.

3. Fixed a regression in the SIMD feature detection code, introduced by
the AVX2 SIMD extensions (2.0 beta1[1]), that caused libjpeg-turbo to crash on
Windows 7 if Service Pack 1 was not installed.

4. Fixed out-of-bounds read in cjpeg that occurred when attempting to compress
a specially-crafted malformed color-index (8-bit-per-sample) Targa file in
which some of the samples (color indices) exceeded the bounds of the Targa
file's color table.

5. Fixed an issue whereby installing a fully static build of libjpeg-turbo
(a build in which `CFLAGS` contains `-static` and `ENABLE_SHARED` is `0`) would
fail with "No valid ELF RPATH or RUNPATH entry exists in the file."


2.0.0
=====

### Significant changes relative to 2.0 beta1:

1. The TurboJPEG API can now decompress CMYK JPEG images that have subsampled M
and Y components (not to be confused with YCCK JPEG images, in which the C/M/Y
components have been transformed into luma and chroma.)   Previously, an error
was generated ("Could not determine subsampling type for JPEG image") when such
an image was passed to `tjDecompressHeader3()`, `tjTransform()`,
`tjDecompressToYUVPlanes()`, `tjDecompressToYUV2()`, or the equivalent Java
methods.

2. Fixed an issue (CVE-2018-11813) whereby a specially-crafted malformed input
file (specifically, a file with a valid Targa header but incomplete pixel data)
would cause cjpeg to generate a JPEG file that was potentially thousands of
times larger than the input file.  The Targa reader in cjpeg was not properly
detecting that the end of the input file had been reached prematurely, so after
all valid pixels had been read from the input, the reader injected dummy pixels
with values of 255 into the JPEG compressor until the number of pixels
specified in the Targa header had been compressed.  The Targa reader in cjpeg
now behaves like the PPM reader and aborts compression if the end of the input
file is reached prematurely.  Because this issue only affected cjpeg and not
the underlying library, and because it did not involve any out-of-bounds reads
or other exploitable behaviors, it was not believed to represent a security
threat.

3. Fixed an issue whereby the `tjLoadImage()` and `tjSaveImage()` functions
would produce a "Bogus message code" error message if the underlying bitmap and
PPM readers/writers threw an error that was specific to the readers/writers
(as opposed to a general libjpeg API error.)

4. Fixed an issue (CVE-2018-1152) whereby a specially-crafted malformed BMP
file, one in which the header specified an image width of 1073741824 pixels,
would trigger a floating point exception (division by zero) in the
`tjLoadImage()` function when attempting to load the BMP file into a
4-component image buffer.

5. Fixed an issue whereby certain combinations of calls to
`jpeg_skip_scanlines()` and `jpeg_read_scanlines()` could trigger an infinite
loop when decompressing progressive JPEG images that use vertical chroma
subsampling (for instance, 4:2:0 or 4:4:0.)

6. Fixed a segfault in `jpeg_skip_scanlines()` that occurred when decompressing
a 4:2:2 or 4:2:0 JPEG image using the merged (non-fancy) upsampling algorithms
(that is, when setting `cinfo.do_fancy_upsampling` to `FALSE`.)

7. The new CMake-based build system will now disable the MIPS DSPr2 SIMD
extensions if it detects that the compiler does not support DSPr2 instructions.

8. Fixed out-of-bounds read in cjpeg (CVE-2018-14498) that occurred when
attempting to compress a specially-crafted malformed color-index
(8-bit-per-sample) BMP file in which some of the samples (color indices)
exceeded the bounds of the BMP file's color table.

9. Fixed a signed integer overflow in the progressive Huffman decoder, detected
by the Clang and GCC undefined behavior sanitizers, that could be triggered by
attempting to decompress a specially-crafted malformed JPEG image.  This issue
did not pose a security threat, but removing the warning made it easier to
detect actual security issues, should they arise in the future.


1.5.90 (2.0 beta1)
==================

### Significant changes relative to 1.5.3:

1. Added AVX2 SIMD implementations of the colorspace conversion, chroma
downsampling and upsampling, integer quantization and sample conversion, and
accurate integer DCT/IDCT algorithms.  When using the accurate integer DCT/IDCT
algorithms on AVX2-equipped CPUs, the compression of RGB images is
approximately 13-36% (avg. 22%) faster (relative to libjpeg-turbo 1.5.x) with
64-bit code and 11-21% (avg. 17%) faster with 32-bit code, and the
decompression of RGB images is approximately 9-35% (avg. 17%) faster with
64-bit code and 7-17% (avg. 12%) faster with 32-bit code.  (As tested on a
3 GHz Intel Core i7.  Actual mileage may vary.)

2. Overhauled the build system to use CMake on all platforms, and removed the
autotools-based build system.  This decision resulted from extensive
discussions within the libjpeg-turbo community.  libjpeg-turbo traditionally
used CMake only for Windows builds, but there was an increasing amount of
demand to extend CMake support to other platforms.  However, because of the
unique nature of our code base (the need to support different assemblers on
each platform, the need for Java support, etc.), providing dual build systems
as other OSS imaging libraries do (including libpng and libtiff) would have
created a maintenance burden.  The use of CMake greatly simplifies some aspects
of our build system, owing to CMake's built-in support for various assemblers,
Java, and unit testing, as well as generally fewer quirks that have to be
worked around in order to implement our packaging system.  Eliminating
autotools puts our project slightly at odds with the traditional practices of
the OSS community, since most "system libraries" tend to be built with
autotools, but it is believed that the benefits of this move outweigh the
risks.  In addition to providing a unified build environment, switching to
CMake allows for the use of various build tools and IDEs that aren't supported
under autotools, including XCode, Ninja, and Eclipse.  It also eliminates the
need to install autotools via MacPorts/Homebrew on OS X and allows
libjpeg-turbo to be configured without the use of a terminal/command prompt.
Extensive testing was conducted to ensure that all features provided by the
autotools-based build system are provided by the new build system.

3. The libjpeg API in this version of libjpeg-turbo now includes two additional
functions, `jpeg_read_icc_profile()` and `jpeg_write_icc_profile()`, that can
be used to extract ICC profile data from a JPEG file while decompressing or to
embed ICC profile data in a JPEG file while compressing or transforming.  This
eliminates the need for downstream projects, such as color management libraries
and browsers, to include their own glueware for accomplishing this.

4. Improved error handling in the TurboJPEG API library:

     - Introduced a new function (`tjGetErrorStr2()`) in the TurboJPEG C API
that allows compression/decompression/transform error messages to be retrieved
in a thread-safe manner.  Retrieving error messages from global functions, such
as `tjInitCompress()` or `tjBufSize()`, is still thread-unsafe, but since those
functions will only throw errors if passed an invalid argument or if a memory
allocation failure occurs, thread safety is not as much of a concern.
     - Introduced a new function (`tjGetErrorCode()`) in the TurboJPEG C API
