sceJpegDecParseHeader and sceJpegDecDecode threw for every down scale
other than 1. SharpProspero's JpegDec.cs documents the factors 1, 2, 4
and 8 and output dimensions that account for the down scale.
Decoder::Jpeg gains DecodeScaled, which decodes through libjpeg-turbo's
scaled inverse DCT, and ScaledDimension, its rounded-up output size.
sceJpegDecParseHeader reports the scaled output size; sceJpegDecDecode
checks the pitch and image buffer against it, writes the scaled image
and packs the output size into its result. A down scale of 1 still
decodes as before. Decode modes other than 0, other down scales and a
down-scaled CMYK or YCCK image still throw.
The libraries are x86-64 code that runs under Rosetta 2 on Apple silicon,
so the full build selects x86-64 itself: CMAKE_OSX_ARCHITECTURES defaults to
x86_64, CMake is told the host processor is x86_64 instead of arm64, and
libjpeg-turbo, which is configured by its own CMake run, gets the same
values. Configuring the full build for another architecture fails with an
error.
Apple clang's libc++ needs -fexperimental-library for the C++20 library
features the sources use.
The prx libraries find each other through their run path. dyld does not
know $ORIGIN, so on macOS it is @loader_path.
Adrià