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DRC fc01f4673b TurboJPEG 3 API overhaul 
(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
2023-01-25 19:09:34 -06:00

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