+ document that tjFree() accepts NULL pointers without complaint.
Effectively, it has had that behavior all along, but the API does not
guarantee that tjFree() will be implemented with free() behind the
scenes, so it's best to formalize the behavior.
Loading RGB image files into a grayscale buffer isn't a particularly
useful feature, given that libjpeg-turbo can perform this conversion
much more optimally (with SIMD acceleration on some platforms) during
the compression process. Also, the RGB2GRAY() macro was not producing
deterministic cross-platform results because of variations in the
round-off behavior of various floating point implementations, so
`tjunittest -bmp` was failing in i386 builds.
Also, set the red/green/blue offsets for TJPF_GRAY to -1 rather than 0.
It was undefined behavior for an application to use those arrays/methods
with TJPF_GRAY anyhow, and this makes it easier for applications to
programmatically detect whether a given pixel format has red, green, and
blue components.
The main justification for this is to provide new libjpeg-turbo users
with a quick & easy way of developing a complete JPEG
compression/decompression program without requiring them to build
libjpeg-turbo from source (which was necessary in order to use the
project-private bmp API) or to use external libraries. These new
functions build upon significant enhancements to rdbmp.c, wrbmp.c,
rdppm.c, and wrppm.c which allow those engines to convert directly
between the native pixel format of the file and a pixel format
("colorspace" in libjpeg parlance) specified by the calling program.
rdbmp.c and wrbmp.c have also been modified such that the calling
program can choose to read or write image rows in the native (bottom-up)
order of the file format, thus eliminating the need to use an inversion
array. tjLoadImage() and tjSaveImage() leverage these new underlying
features in order to significantly improve upon the performance of the
old bmp API.
Because these new functions cannot work without the libjpeg-turbo
colorspace extensions, the libjpeg-compatible code in turbojpeg.c has
been removed. That code was only there to serve as an example of how
to use the TurboJPEG API on top of libjpeg, but more specific, buildable
examples now exist in the https://github.com/libjpeg-turbo/ijg
repository.
Allow progressive entropy coding to be enabled on a
transform-by-transform basis, and implement a new transform option for
disabling the copying of markers.
Closes#153
If the source image for a transform operation has a lot of EXIF or ICC
data embedded in it, then it may cause the output image size to exceed
the worst-case size returned by tjBufSize() (because tjTransform()
transfers all markers to the output image.) This is only a problem if
TJFLAG_NOREALLOC is passed to the function. Since the TurboJPEG C API
doesn't require the destination image size to be set in this case, it
makes the documented assumption that the calling program has allocated
the destination buffer to exactly the size returned by tjBufSize().
Changing this assumption would change the API behavior and necessitate
a new function name (tjTransform2().) At the moment, it's easier to
just document this as a known issue, since it's easy to work around in
the C API.
The Java API is unfortunately a different story, since it must always
use TJFLAG_NOREALLOC (because, when using the TurboJPEG Java API, all
buffers are allocated on the Java heap, and thus they can't be
reallocated by the C code.) There is no easy way to work around this
without changing the C API as discussed above, because if the source
image contains large amounts of marker data, it's virtually impossible
to determine how big the output image will be.
- Provide a new C API function and TJException method that allows
calling programs to query the severity of a compression/decompression/
transform error.
- Provide a new flag that instructs the library to immediately stop
compressing/decompressing/transforming if a warning is encountered.
Fixes#151
Introduce a new C API function (tjGetErrorStr2()) that can be used to
retrieve compression/decompression/transform error messages in a
thread-safe (i.e. instance-specific) manner. Retrieving error messages
from global functions is still thread-unsafe.
Addresses a concern expressed in #151.
The changes relative to 1.4.x are only cosmetic (using const pointers)
and should not affect API/ABI compatibility, but our practice is to
synchronize the API revision with the most recent release that provides
user-visible changes to the API.
This reassures the caller that the buffers will not be modified and also
allows read-only buffers to be passed to the functions.
Partially reverts 3947a19f25fc8186d3812dbcf8e70baea36ef652.
