With rare exceptions ...
- Always separate line continuation characters by one space from
preceding code.
- Always use two-space indentation. Never use tabs.
- Always use K&R-style conditional blocks.
- Always surround operators with spaces, except in raw assembly code.
- Always put a space after, but not before, a comma.
- Never put a space between type casts and variables/function calls.
- Never put a space between the function name and the argument list in
function declarations and prototypes.
- Always surround braces ('{' and '}') with spaces.
- Always surround statements (if, for, else, catch, while, do, switch)
with spaces.
- Always attach pointer symbols ('*' and '**') to the variable or
function name.
- Always precede pointer symbols ('*' and '**') by a space in type
casts.
- Use the MIN() macro from jpegint.h within the libjpeg and TurboJPEG
API libraries (using min() from tjutil.h is still necessary for
TJBench.)
- Where it makes sense (particularly in the TurboJPEG code), put a blank
line after variable declaration blocks.
- Always separate statements in one-liners by two spaces.
The purpose of this was to ease maintenance on my part and also to make
it easier for contributors to figure out how to format patch
submissions. This was admittedly confusing (even to me sometimes) when
we had 3 or 4 different style conventions in the same source tree. The
new convention is more consistent with the formatting of other OSS code
bases.
This commit corrects deviations from the chosen formatting style in the
libjpeg API code and reformats the TurboJPEG API code such that it
conforms to the same standard.
NOTES:
- Although it is no longer necessary for the function name in function
declarations to begin in Column 1 (this was historically necessary
because of the ansi2knr utility, which allowed libjpeg to be built
with non-ANSI compilers), we retain that formatting for the libjpeg
code because it improves readability when using libjpeg's function
attribute macros (GLOBAL(), etc.)
- This reformatting project was accomplished with the help of AStyle and
Uncrustify, although neither was completely up to the task, and thus
a great deal of manual tweaking was required. Note to developers of
code formatting utilities: the libjpeg-turbo code base is an
excellent test bed, because AFAICT, it breaks every single one of the
utilities that are currently available.
- The legacy (MMX, SSE, 3DNow!) assembly code for i386 has been
formatted to match the SSE2 code (refer to
ff5685d5344273df321eb63a005eaae19d2496e3.) I hadn't intended to
bother with this, but the Loongson MMI implementation demonstrated
that there is still academic value to the MMX implementation, as an
algorithmic model for other 64-bit vector implementations. Thus, it
is desirable to improve its readability in the same manner as that of
the SSE2 implementation.
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.
- Referring to 073b0e88a1 and #185, the
reason why BMP and RLE didn't (and won't) work with partial image
decompression is that the output engines for both formats maintain a
whole-image buffer, which is used to reverse the order of scanlines.
However, it was straightforward to add -crop support for GIF and
Targa, which is useful for testing partial image decompression along
with color quantization.
- Such testing reproduced a bug reported by Mozilla (refer to PR #182)
whereby jpeg_skip_scanlines() would segfault if color quantization was
enabled. To fix this issue, read_and_discard_scanlines() now sets up
a dummy quantize function in the same manner that it sets up a dummy
color conversion function.
Closes#182
... and document that only PPM/PGM output images are supported with the
-crop option for the moment.
I investigated the possibility of supporting -crop with -bmp, but even
after resetting the buffer dimensions, I still kept getting virtual
array access errors. It seems that doing this the "right way" would
require creating a re-initialization function for each image format's
destination manager. I'm disinclined to do that right now, given that
this feature was Google's baby (developed as a prerequisite for
including libjpeg-turbo in Android), and the -crop option in djpeg is
intended only as an example of how to use the partial image
decompression API. Real-world applications would need to handle this
in their own destination managers.
It would probably be possible to make this work with Targa by employing
a similar hack to the one we used with PPM, but Targa isn't popular
enough to bother.
Fixes#185
This commit does the following:
-- Merges the two glueware functions (read_icc_profile() and
write_icc_profile()) from iccjpeg.c, which is contained in downstream
projects such as LCMS, Ghostscript, Mozilla, etc. These functions were
originally intended for inclusion in libjpeg, but Tom Lane left the IJG
before that could be accomplished. Since then, programs and libraries
that needed to embed/extract ICC profiles in JPEG files had to include
their own local copy of iccjpeg.c, which is suboptimal.
-- The new functions were prefixed with jpeg_ and split into separate
files for the compressor and decompressor, per the existing libjpeg
coding standards.
-- jpeg_write_icc_profile() was made slightly more fault-tolerant.
It will now trigger a libjpeg error if it is called before
jpeg_start_compress() or if it is passed NULL arguments.
-- jpeg_read_icc_profile() was made slightly more fault-tolerant.
It will now trigger a libjpeg error if it is called before
jpeg_read_header() or if it is passed NULL arguments. It will also
now trigger libjpeg warnings if the ICC profile data is corrupt.
-- The code comments have been wordsmithed.
-- Note that the one-line setup_read_icc_profile() function was not
included. Instead, libjpeg.txt now documents the need to call
jpeg_save_markers(cinfo, JPEG_APP0 + 2, 0xFFFF) prior to calling
jpeg_read_header(), if jpeg_read_icc_profile() is to be used.
-- Adds documentation for the new functions to libjpeg.txt.
-- Adds an -icc switch to cjpeg and jpegtran that allows those programs
to embed an ICC profile in the JPEG files they generate.
-- Adds an -icc switch to djpeg that allows that program to extract an
ICC profile from a JPEG file while decompressing.
-- Adds appropriate unit tests for all of the above.
-- Bumps the SO_AGE of the libjpeg API library to indicate the presence
of new API functions.
Note that the licensing information was obtained from:
https://github.com/mm2/Little-CMS/issues/37#issuecomment-66450180
This, in combination with the existing jpeg_skip_scanlines() function,
provides the ability to crop the image both horizontally and vertically
while decompressing (certain restrictions apply-- see libjpeg.txt.)
This also cleans up the documentation of the line skipping feature and
removes the "strip decompression" feature from djpeg, since the new
cropping feature is a superset of it.
Refer to #34 for discussion.
Closes#34
The convention used by libjpeg:
type * variable;
is not very common anymore, because it looks too much like
multiplication. Some (particularly C++ programmers) prefer to tuck the
pointer symbol against the type:
type* variable;
to emphasize that a pointer to a type is effectively a new type.
However, this can also be confusing, since defining multiple variables
on the same line would not work properly:
type* variable1, variable2; /* Only variable1 is actually a
pointer. */
This commit reformats the entirety of the libjpeg-turbo code base so
that it uses the same code formatting convention for pointers that the
TurboJPEG API code uses:
type *variable1, *variable2;
This seems to be the most common convention among C programmers, and
it is the convention used by other codec libraries, such as libpng and
libtiff.
These days, INT32 is a commonly-defined datatype in system headers. We
cannot eliminate the definition of that datatype from jmorecfg.h, since
the INT32 typedef has technically been part of the libjpeg API since
version 5 (1994.) However, using INT32 internally is risky, because the
inclusion of a particular header (Xmd.h, for instance) could change the
definition of INT32 from long to int on 64-bit platforms and thus change
the internal behavior of libjpeg-turbo in unexpected ways (for instance,
failing to correctly set __INT32_IS_ACTUALLY_LONG to match the INT32
typedef-- perhaps as a result of including the wrong version of
jpeglib.h-- could cause libjpeg-turbo to produce incorrect results.)
The library has always been built in environments in which INT32 is
effectively long (on Windows, long is always 32-bit, so effectively it's
the same as int), so it makes sense to turn INT32 into an explicitly
long datatype. This ensures that libjpeg-turbo will always behave
consistently, regardless of the headers included at compile time.
Addresses a concern expressed in #26.
The IJG README file has been renamed to README.ijg, in order to avoid
confusion (many people were assuming that that was our project's README
file and weren't reading README-turbo.txt) and to lay the groundwork for
markdown versions of the libjpeg-turbo README and build instructions.
-- Auto-generates HAVE_LOCALE_H macro and adds it to jconfig.h (this is used by rdjpgcom.c.)
-- Reconciles the description and ordering of macros between config.h.in and jconfig.h.in, so the two files can be easily diffed.
-- Eliminates the use of the autoheader-generated config.h in the project and moves relevant internal-only macros into a new file, jconfigint.h. This is to avoid "already defined" warnings in files that were including both config.h (to get the internal autotools package information or the INLINE definition) and jconfig.h.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1258 632fc199-4ca6-4c93-a231-07263d6284db
