... caused by using certain specific combinations of
jpeg_skip_scanlines() and jpeg_read_scanlines() calls with progressive,
vertically-subsampled JPEG images.
Fixes#237
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.
If jpeg_skip_scanlines() is used to skip to the end of a single-scan
image, then we need to change the library state such that subsequent
calls to jpeg_consume_input() will return JPEG_REACHED_EOI rather than
JPEG_SUSPENDED. (NOTE: not necessary for multi-scan images, since the
scans are processed prior to any call to jpeg_skip_scanlines().)
Unless I miss my guess, using jpeg_skip_scanlines() in this manner
will prevent any markers at the end of the JPEG image from being
read, but I don't think there is any way around that without actually
reading the data, which would defeat the purpose of
jpeg_skip_scanlines().
Fixes#194
- 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
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
jinclude.h can't be safely included multiple times, so instead of
including it in the shared (broken-out) headers, it should instead be
included by the source files that include one or more of those headers.
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.
When using context-based upsampling, use a dummy color conversion
routine instead of a dummy row buffer. This improves performance
(since the actual color conversion routine no longer has to be called),
and it also fixes valgrind errors when decompressing to RGB565.
Valgrind previously complained, because using the RGB565 color
converter with the dummy row buffer was causing a table lookup with
undefined indices.
