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README.md, package specs: Various tweaks
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- Don't enumerate the types of SIMD instructions that libjpeg-turbo
  supports, as this can change without notice.
- Use more clear terminology when describing support for libjpeg v7/v8
  features ("libjpeg" is, colloquially but not officially, the name for
  the IJG's software, whereas the "libjpeg API" refers to our emulation
  of said software.)
- "PhotoShop" = "Photoshop" (StudLy Caps Police)
- Adjust dynamic library versions to reflect the addition of
  jpeg_read_icc_profile() and jpeg_write_icc_profile() in
  libjpeg-turbo 2.0.x.
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dcommander committed Dec 31, 2019
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34 changes: 17 additions & 17 deletions README.md
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Background
==========

libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2,
AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression
on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG
compression on x86 and x86-64 systems. On such systems, libjpeg-turbo is
generally 2-6x as fast as libjpeg, all else being equal. On other types of
systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by
virtue of its highly-optimized Huffman coding routines. In many cases, the
performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.
libjpeg-turbo is a JPEG image codec that uses SIMD instructions to accelerate
baseline JPEG compression and decompression on x86, x86-64, ARM, PowerPC, and
MIPS systems, as well as progressive JPEG compression on x86 and x86-64
systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg,
all else being equal. On other types of systems, libjpeg-turbo can still
outperform libjpeg by a significant amount, by virtue of its highly-optimized
Huffman coding routines. In many cases, the performance of libjpeg-turbo
rivals that of proprietary high-speed JPEG codecs.

libjpeg-turbo implements both the traditional libjpeg API as well as the less
powerful but more straightforward TurboJPEG API. libjpeg-turbo also features
Expand Down Expand Up @@ -145,14 +145,14 @@ supported and which aren't.

#### Fully supported

- **libjpeg: IDCT scaling extensions in decompressor**<br>
- **libjpeg API: IDCT scaling extensions in decompressor**<br>
libjpeg-turbo supports IDCT scaling with scaling factors of 1/8, 1/4, 3/8,
1/2, 5/8, 3/4, 7/8, 9/8, 5/4, 11/8, 3/2, 13/8, 7/4, 15/8, and 2/1 (only 1/4
and 1/2 are SIMD-accelerated.)

- **libjpeg: Arithmetic coding**
- **libjpeg API: Arithmetic coding**

- **libjpeg: In-memory source and destination managers**<br>
- **libjpeg API: In-memory source and destination managers**<br>
See notes below.

- **cjpeg: Separate quality settings for luminance and chrominance**<br>
Expand Down Expand Up @@ -184,14 +184,14 @@ means of quality improvement. The reader is invited to peruse the research at
but it is the general belief of our project that these features have not
demonstrated sufficient usefulness to justify inclusion in libjpeg-turbo.

- **libjpeg: DCT scaling in compressor**<br>
- **libjpeg API: DCT scaling in compressor**<br>
`cinfo.scale_num` and `cinfo.scale_denom` are silently ignored.
There is no technical reason why DCT scaling could not be supported when
emulating the libjpeg v7+ API/ABI, but without the SmartScale extension (see
below), only scaling factors of 1/2, 8/15, 4/7, 8/13, 2/3, 8/11, 4/5, and
8/9 would be available, which is of limited usefulness.

- **libjpeg: SmartScale**<br>
- **libjpeg API: SmartScale**<br>
`cinfo.block_size` is silently ignored.
SmartScale is an extension to the JPEG format that allows for DCT block
sizes other than 8x8. Providing support for this new format would be
Expand All @@ -204,7 +204,7 @@ demonstrated sufficient usefulness to justify inclusion in libjpeg-turbo.
interest in providing this feature would be as a means of supporting
additional DCT scaling factors.

- **libjpeg: Fancy downsampling in compressor**<br>
- **libjpeg API: Fancy downsampling in compressor**<br>
`cinfo.do_fancy_downsampling` is silently ignored.
This requires the DCT scaling feature, which is not supported.

Expand Down Expand Up @@ -252,8 +252,8 @@ building libjpeg-turbo. This will restore the pre-1.3 behavior, in which
libjpeg v8 API/ABI.

On Un*x systems, including the in-memory source/destination managers changes
the dynamic library version from 62.1.0 to 62.2.0 if using libjpeg v6b API/ABI
emulation and from 7.1.0 to 7.2.0 if using libjpeg v7 API/ABI emulation.
the dynamic library version from 62.2.0 to 62.3.0 if using libjpeg v6b API/ABI
emulation and from 7.2.0 to 7.3.0 if using libjpeg v7 API/ABI emulation.

Note that, on most Un*x systems, the dynamic linker will not look for a
function in a library until that function is actually used. Thus, if a program
Expand Down Expand Up @@ -329,7 +329,7 @@ in a way that makes the rest of the libjpeg infrastructure happy, so it is
necessary to use the slow Huffman decoder when decompressing a JPEG image that
has restart markers. This can cause the decompression performance to drop by
as much as 20%, but the performance will still be much greater than that of
libjpeg. Many consumer packages, such as PhotoShop, use restart markers when
libjpeg. Many consumer packages, such as Photoshop, use restart markers when
generating JPEG images, so images generated by those programs will experience
this issue.

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2 changes: 1 addition & 1 deletion release/ReadMe.txt
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libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2, AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG compression on x86 and x86-64 systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg, all else being equal. On other types of systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by virtue of its highly-optimized Huffman coding routines. In many cases, the performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.
libjpeg-turbo is a JPEG image codec that uses SIMD instructions to accelerate baseline JPEG compression and decompression on x86, x86-64, ARM, PowerPC, and MIPS systems, as well as progressive JPEG compression on x86 and x86-64 systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg, all else being equal. On other types of systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by virtue of its highly-optimized Huffman coding routines. In many cases, the performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.

libjpeg-turbo implements both the traditional libjpeg API as well as the less powerful but more straightforward TurboJPEG API. libjpeg-turbo also features colorspace extensions that allow it to compress from/decompress to 32-bit and big-endian pixel buffers (RGBX, XBGR, etc.), as well as a full-featured Java interface.

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17 changes: 8 additions & 9 deletions release/deb-control.in
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Expand Up @@ -8,15 +8,14 @@ Maintainer: @PKGVENDOR@ <@PKGEMAIL@>
Homepage: @PKGURL@
Installed-Size: {__SIZE}
Description: A SIMD-accelerated JPEG codec that provides both the libjpeg and TurboJPEG APIs
libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2,
AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression
on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG
compression on x86 and x86-64 systems. On such systems, libjpeg-turbo is
generally 2-6x as fast as libjpeg, all else being equal. On other types of
systems, libjpeg-turbo can still outperform libjpeg by a significant amount,
by virtue of its highly-optimized Huffman coding routines. In many cases, the
performance of libjpeg-turbo rivals that of proprietary high-speed JPEG
codecs.
libjpeg-turbo is a JPEG image codec that uses SIMD instructions to accelerate
baseline JPEG compression and decompression on x86, x86-64, ARM, PowerPC, and
MIPS systems, as well as progressive JPEG compression on x86 and x86-64
systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg,
all else being equal. On other types of systems, libjpeg-turbo can still
outperform libjpeg by a significant amount, by virtue of its highly-optimized
Huffman coding routines. In many cases, the performance of libjpeg-turbo
rivals that of proprietary high-speed JPEG codecs.
.
libjpeg-turbo implements both the traditional libjpeg API as well as the less
powerful but more straightforward TurboJPEG API. libjpeg-turbo also features
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16 changes: 8 additions & 8 deletions release/rpm.spec.in
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Expand Up @@ -51,14 +51,14 @@ Provides: %{name} = %{version}-%{release}, @CMAKE_PROJECT_NAME@ = %{version}-%{r
%endif

%description
libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2,
AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression
on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG
compression on x86 and x86-64 systems. On such systems, libjpeg-turbo is
generally 2-6x as fast as libjpeg, all else being equal. On other types of
systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by
virtue of its highly-optimized Huffman coding routines. In many cases, the
performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.
libjpeg-turbo is a JPEG image codec that uses SIMD instructions to accelerate
baseline JPEG compression and decompression on x86, x86-64, ARM, PowerPC, and
MIPS systems, as well as progressive JPEG compression on x86 and x86-64
systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg,
all else being equal. On other types of systems, libjpeg-turbo can still
outperform libjpeg by a significant amount, by virtue of its highly-optimized
Huffman coding routines. In many cases, the performance of libjpeg-turbo
rivals that of proprietary high-speed JPEG codecs.

libjpeg-turbo implements both the traditional libjpeg API as well as the less
powerful but more straightforward TurboJPEG API. libjpeg-turbo also features
Expand Down

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