The Gordian knot that 7fec5074f9 attempted
to unravel was caused by the fact that there are several
data-precision-dependent (JSAMPLE-dependent) fields and methods in the
exposed libjpeg API structures, and if you change the exposed libjpeg
API structures, then you have to change the whole API. If you change
the whole API, then you have to provide a whole new library to support
the new API, and that makes it difficult to support multiple data
precisions in the same application. (It is not impossible, as example.c
demonstrated, but using data-precision-dependent libjpeg API structures
would have made the cjpeg, djpeg, and jpegtran source code hard to read,
so it made more sense to build, install, and package 12-bit-specific
versions of those applications.)
Unfortunately, the result of that initial integration effort was an
unreadable and unmaintainable mess, which is a problem for a library
that is an ISO/ITU-T reference implementation. Also, as I dug into the
problem of lossless JPEG support, I realized that 16-bit lossless JPEG
images are a thing, and supporting yet another version of the libjpeg
API just for those images is untenable.
In fact, however, the touch points for JSAMPLE in the exposed libjpeg
API structures are minimal:
- The colormap and sample_range_limit fields in jpeg_decompress_struct
- The alloc_sarray() and access_virt_sarray() methods in
jpeg_memory_mgr
- jpeg_write_scanlines() and jpeg_write_raw_data()
- jpeg_read_scanlines() and jpeg_read_raw_data()
- jpeg_skip_scanlines() and jpeg_crop_scanline()
(This is subtle, but both of those functions use JSAMPLE-dependent
opaque structures behind the scenes.)
It is much more readable and maintainable to provide 12-bit-specific
versions of those six top-level API functions and to document that the
aforementioned methods and fields must be type-cast when using 12-bit
samples. Since that eliminates the need to provide a 12-bit-specific
version of the exposed libjpeg API structures, we can:
- Compile only the precision-dependent libjpeg modules (the
coefficient buffer controllers, the colorspace converters, the
DCT/IDCT managers, the main buffer controllers, the preprocessing
and postprocessing controller, the downsampler and upsamplers, the
quantizers, the integer DCT methods, and the IDCT methods) for
multiple data precisions.
- Introduce 12-bit-specific methods into the various internal
structures defined in jpegint.h.
- Create precision-independent data type, macro, method, field, and
function names that are prefixed by an underscore, and use an
internal header to convert those into precision-dependent data
type, macro, method, field, and function names, based on the value
of BITS_IN_JSAMPLE, when compiling the precision-dependent libjpeg
modules.
- Expose precision-dependent jinit*() functions for each of the
precision-dependent libjpeg modules.
- Abstract the precision-dependent libjpeg modules by calling the
appropriate precision-dependent jinit*() function, based on the
value of cinfo->data_precision, from top-level libjpeg API
functions.
- Fix an issue whereby a build with ENABLE_SHARED=0 could not be
installed when using the Ninja Multi-Config CMake generator.
- Fix an issue whereby a Windows installer could not be built when using
the Ninja Multi-Config CMake generator.
- Fix an issue whereby the Java regression tests failed when using the
Ninja Multi-Config CMake generator.
Based on:
4f169deeb0Closes#626
When 12-bit-per-component JPEG support is enabled (WITH_12BIT=1) or the
TurboJPEG API library and associated test programs are disabled
(WITH_TURBOJPEG=0), the Windows installer target should not depend on
the turbojpeg, turbojpeg-static, and tjbench targets.
Arm compilers have three floating point ABI options:
'soft' compiles floating point operations as function calls into a
software floating point library, which emulates floating point
operations using integer operations. Floating point function arguments
are passed using integer registers.
'softfp' also compiles floating point operations as function calls into
a floating point library and passes floating point function arguments
using integer registers, but the floating point library functions can
use FPU instructions if the CPU supports them.
'hard' compiles floating point operations into inline FPU instructions,
similarly to x86 and other architectures, and passes floating point
function arguments using FPU registers.
Not all AArch32 CPUs have FPUs or support Neon instructions, so on Linux
and Android platforms, the AArch32 SIMD dispatcher in libjpeg-turbo only
enables the Neon SIMD extensions at run time if /proc/cpuinfo indicates
that the CPU supports Neon instructions or if Neon instructions are
explicitly enabled (e.g. by passing -mfpu=neon to the compiler.) In
order to support all AArch32 CPUs using the same code base, i.e. to
support run-time FPU and Neon auto-detection, it is necessary to compile
the scalar C source code using -mfloat-abi=soft. However, the 'soft'
floating point ABI cannot be used when compiling Neon intrinsics, so the
intrinsics implementation of the Neon SIMD extensions must be compiled
using -mfloat-abi=softfp if the scalar C source code is compiled using
-mfloat-abi=soft.
This commit modifies the build system so that it detects whether
-mfloat-abi=softfp must be explicitly added to the compiler flags when
building the intrinsics implementation of the Neon SIMD extensions.
This will be necessary if the build is using the 'soft' floating
point ABI along with run-time auto-detection of Neon instructions.
Fixes#523
- Rename IOS_ARMV8_BUILD to ARMV8_BUILD.
- Rename install_ios() to install_subbuild() in makemacpkg.
- Wordsmith the build instructions accordingly.
- Use xcode12.2 image in Travis CI.
- Set CPU_TYPE=arm if performing a 32-bit build on an AArch64 system.
This eliminates the need to use a CMake toolchain file.
- Set RPMARCH=armv7hl if building on a 32-bit Arm system with an FPU.
- Set RPMARCH=armv7hl and DEBARCH=armhf if performing a 32-bit build
using a gnueabihf toolchain.
- If performing a 32-bit Arm build, generate a 32-bit supplementary DEB
package for AArch64 systems.
The scales have now tilted overwhelmingly in favor of eliminating
support for 32-bit Macs:
- 32-bit applications are only necessary in order to support OS X 10.5
"Leopard" and OS X 10.6 "Snow Leopard". OS X 10.7 "Lion" requires a
64-bit Mac and supports all 64-bit Macs.
- 32-bit applications are no longer allowed in the macOS App Store.
- 32-bit applications no longer run in macOS 10.15 "Catalina".
- 32-bit applications do not support thread-local storage, so the
TurboJPEG API library's global error handler is not thread-safe with
such applications.
- libjpeg-turbo 2.1.x no longer supports 32-bit iOS apps, so it makes
sense to also eliminate support for 32-bit macOS applications.
It's time.
We haven't provided official Cygwin builds since 1.4.x, since Cygwin
now supplies its own libjpeg-turbo packages (although they apparently
haven't been updated past 1.5.3.)
- Replace CMAKE_SOURCE_DIR with CMAKE_CURRENT_SOURCE_DIR
- Replace CMAKE_BINARY_DIR with CMAKE_CURRENT_BINARY_DIR
- Don't use "libjpeg-turbo" in any of the package system filenames
(because CMAKE_PROJECT_NAME will not be the same if building LJT as
a submodule.)
Closes#122
