If the data precision of the PBMPLUS file does not match the target data
precision, then the grayscale or RGB samples are rescaled to the target
data precision. Thus, we need to pass (1 << cinfo->data_precision) - 1
to rgb_to_cmyk() instead of maxval. This commit also modifies
TJUnitTest so that it validates the correctness of upconversion and
downconversion in the PPM reader.
Fixes#841
If loading a 2-to-8-bit image, unset srcBuf12 and srcBuf16. If loading
a 9-to-12-bit image, unset srcBuf8 and srcBuf16. If loading a
13-to-16-bit image, unset srcBuf8 and srcBuf12. Otherwise,
TJCompressor.getSourceBuf() will return srcBuf8 or srcBuf12, in order,
if any previous invocation of TJCompressor.loadSourceImage() set them,
irrespective of the buffer that was set by the most recent invocation.
This probably helps with garbage collection as well, since it signals to
the GC that the unused buffers are really unused.
This is not a security vulnerability, since applications that pass such
values to the Java API would fail regardless, and such a bug would never
make it into the wild. By contrast, a security vulnerability arises
from applications that work correctly with most input data sets but
trigger a library failure, such as a buffer overrun, with one or more
specific input data sets. As with most imaging APIs, the libjpeg-turbo
APIs rely upon the calling application to pass appropriately-sized
buffers and appropriate size/dimension arguments. The failure to do so
is no more the fault of libjpeg-turbo than calling
'buf = malloc(1); buf[2] = 0;' is the fault of the C library.
Buffer size checking is a bonus feature of the Java API that isn't (and
can't be) provided by the C API, so this commit merely hardens the bonus
feature against API abuse, in keeping with the Java paradigm of throwing
an exception rather than crashing due to a caller-imposed buffer
overrun.
- Clarify that YUV encoding performs downsampling as well as color
conversion.
- Clarify that TJPARAM_LOSSLESS is ignored by tj3CompressFromYUV*8().
- Clarify that tj3CompressFromYUV*8() generates only YCbCr or grayscale
JPEG images, i.e. that TJPARAM_COLORSPACE has no effect.
This is subtle, but #include <header.h> searches directories specified
with -I, then system include directories. #include "header.h" searches
the current source directory, then directories specified with -I, then
system include directories.
Using bracketed #include directives for jpeglib.h, jinclude.h, jerror.h,
cdjpeg.h, and turbojpeg.h only worked because the build system
explicitly passed -I{source_directory}/src/ to the compiler. Referring
to 51cee03629, it's better for the source
code to have as few dependencies on our specific build system as
possible.
Since jpeglib.h, jinclude.h, jerror.h, and turbojpeg.h can be installed
in system include directories, it's also better for internal references
to those headers to resolve internally first, to avoid potential
conflicts between the system-installed version of libjpeg-turbo and the
version being built. (Such conflicts would never have occurred with our
build system, but they might have occurred due to misintegration with a
downstream build system.)
Since libjpeg-turbo does not support Exif, the only way it can embed
density information in a JPEG image is by using the JFIF marker, which
is only written if the JPEG colorspace is YCbCr or grayscale.
(Referring to the conversation under #793, we may need to further
restrict that to 8-bit-per-sample JPEG images, because the JFIF spec
requires 8-bit data precision.)
This is just a code readability thing. The logic effectively caused the
data precision to default to 8 if -precision was not specified, but that
was not obvious.
This commit also modifies tjcomptest so that it tests TJComp with no
-precision argument, to ensure that the data precision defaults to 8.
Since the introduction of TJFLAG_NOREALLOC in libjpeg-turbo 1.2.x, the
TurboJPEG C API documentation has (confusingly) stated that:
- if the JPEG buffer pointer points to a pre-allocated buffer, then the
JPEG buffer size must be specified, and
- the JPEG buffer size should be specified if the JPEG buffer is
pre-allocated to an arbitrary size.
The documentation never explicitly stated that the JPEG buffer size
should be specified if the JPEG buffer is pre-allocated to a worst-case
size, but since focus does not imply exclusion, it also never explicitly
stated the reverse. Furthermore, the documentation never stated that
this was contingent upon TJPARAM_NOREALLOC/TJFLAG_NOREALLOC. However,
effectively the compression and lossless transformation functions
ignored the JPEG buffer size(s) passed to them, and assumed that the
JPEG buffer(s) had been allocated to a worst-case size, if
TJPARAM_NOREALLOC/TJFLAG_NOREALLOC was set. This behavior was an
accidental and undocumented throwback to libjpeg-turbo 1.1.x, in which
the tjCompress() function provided no way to specify the JPEG buffer
size. It was always a bad idea for applications to rely upon that
behavior (although our own TJBench application unfortunately did.)
However, if such applications exist in the wild, the new behavior would
constitute a breaking change, so it has been introduced only into
libjpeg-turbo 3.1.x and only into TurboJPEG 3 API functions. The
previous behavior has been retained when calling functions from the
TurboJPEG 2.1.x API and prior versions.
Did I mention that APIs are hard?
With respect to tj3Transform(), this addresses an oversight from
bb1d540a80.
Note to self: A convenience function/method for computing the worst-case
transformed JPEG size for a particular transform would be nice.
- When transforming, the worst-case JPEG buffer size depends on the
subsampling level used in the destination image, since a grayscale
transform might have been applied.
- Parentheses Police
-copynone --> -copy none
Add '-copy all', even though it's the default.
-rgb, -bgr, -rgbx, -bgrx, -xbgr, -xrgb, -gray, -cmyk -->
-pixelformat {rgb|bgr|rgbx|bgrx|xbgr|xrgb|gray|cmyk}
(This is mainly so -gray won't interfere with -grayscale.)
Fix an ArrayIndexOutOfBoundsException that occurred when passing -dct
to the Java version without specifying the DCT algorithm (oversight from
24fbf64d31a0758c63bcc27cf5d92fc5611717d0.)
Lossless cropping is performed after other lossless transform
operations, so the cropping region must be specified relative to the
destination image dimensions and level of chrominance subsampling, not
the source image dimensions and level of chrominance subsampling.
More specifically, if the lossless transform operation swaps the X and Y
axes, or if the image is converted to grayscale, then that changes the
cropping region requirements.
The JPEG-1 spec never uses the term "MCU block". That term is rarely
used in other literature to describe the equivalent of an MCU in an
interleaved JPEG image, but the libjpeg documentation uses "iMCU" to
describe the same thing. "iMCU" is a better term, since the equivalent
of an interleaved MCU can contain multiple DCT blocks (or samples in
lossless mode) that are only grouped together if the image is
interleaved.
In the case of restart markers, "MCU block" was used in the libjpeg
documentation instead of "MCU", but "MCU" is more accurate and less
confusing. (The restart interval is literally in MCUs, where one MCU
is one data unit in a non-interleaved JPEG image and multiple data units
in a multi-component interleaved JPEG image.)
In the case of 9b704f96b2, the issue was
actually with progressive JPEG images exactly two DCT blocks wide, not
two MCU blocks wide.
This commit also defines "MCU" and "MCU row" in the description of the
various restart marker options/parameters. Although an MCU row is
technically always a row of samples in lossless mode, "sample row" was
confusing, since it is used in other places to describe a row of samples
for a single component (whereas an MCU row in a typical lossless JPEG
image consists of a row of interleaved samples for all components.)
TJ*PARAM_RESTARTBLOCKS technically works with lossless compression, but
it is not useful, since the value must be equal to the number of samples
in a row. (In other words, it is no different than
TJ*PARAM_RESTARTINROWS, except that it requires the user to do more
math.)
Due to an oversight in the multi-precision feature,
TJCompressor.srcBuf12 and TJCompressor.srcBuf16 were not set to null
in TJCompressor.setSourceImage(YUVImage) or
TJCompressor.setSourceImage(BufferedImage, ...). Thus, if an
application set a 12-bit or 16-bit packed-pixel buffer as the source
image then set a BufferedImage with integer pixels as the source image,
TJCompress.compress() would compress from the 12-bit or 16-bit
packed-pixel buffer instead of the BufferedImage. The odds of an
application actually doing that are very slim, however.
... using the same matching algorithm as cjpeg/djpeg/jpegtran and, where
possible, the same abbreviations:
-a for -arithmetic
-b for -bmp
-cr for -crop
-g for -grayscale
-l for -lossless
-max for -maxmemory
-o for -optimize
-pre for -precision
-p for -progressive
-r for -restart
-s for -scale
-t for -transpose
-transv for -transverse
