libjpeg-turbo turns on dithering by default. When we
decode to RGBA, it uses Floyd-Steinberg dithering -
consistent with the libjpeg6b gold standard,
When we decode to 565, it uses ordered dithering. Ordered
dithering for 565 is not part of the 6b standard (libjpeg6b
doesn't even support 565) and is causing us a number of
issues:
(1) Ordered dithering + nearest neighbor sampling is
causing checkerboard visual artifacts in some outputs.
(2) The ordered dither function in libjpeg-turbo actually
behaves differently depending on the alignment of the
memory that it decodes into. This means that two image
decodes that should be identical may look different just
because they decode into different memory blocks. This
was causing some diffs on Gold with the scanline_subset
test that were causing me some confusion.
(3) Maybe not the best evidence, but visually I can't tell
a difference with and without dithering (except when
nearest neighbor scaling causes the checkerboard artifact).
(4) Turning off dithering should be a more significant
performance improvement than you might expect.
libjpeg-turbo has SIMD color conversions to 565, but when
dithering is on, it defaults to scalar code.
This CL should make every jpeg decode to 565 on Gold look
slightly different. Yay!
BUG=skia:
Review URL: https://codereview.chromium.org/1349563007
Redesigns SkScanlineDecoder.h to indicate the ordering
in which the scanlines are provided
Refactors SkSwizzler::Fill() to include the zeroInit check
and to actually be correct.
BUG=skia:3257
BUG=skia:4198
Review URL: https://codereview.chromium.org/1287423002
We don't want to test small images on Gold because they are
not interested to look at. Instead, I wrote a unit test to
verify that scaling small images does not cause crashes.
BUG=skia:
Review URL: https://codereview.chromium.org/1287863004
Add more swizzling functions for swizzling to 565. Much of this
code was revived from crrev.com/1055743003 (for BMP). Also added
swizzling functions for WBMP.
Consolidate the static function conversion_possible.
In SkCodec::getPixels, check that the alphatype corresponds to the
colorType. This prevents requesting 565 + non-opaque.
In SkIcoCodec, report that the image is unpremul (instead of
whatever the largest embedded codec thinks), but modify the
requested info to have the alpha type expected/required by the
embedded codec.
Add tests for decoding to 565.
BUG=skia:3257
BUG=skia:3683
Review URL: https://codereview.chromium.org/1277213002
Add a static function to CodexTest, which consolidates decoding,
comparing to an expected SkCodec::Result, and optionally comparing to a
digest.
Test decoding non-opaque to opaque (fails) and premul to unpremul/vice
versa (succeeds).
BUG=skia:3475
Review URL: https://codereview.chromium.org/1277253003
Chromium's test suite contains an RLE image that reports a certain
file size in the header, but then contains additional encoded data.
Our bmp decoder would only decode half of the image, before stopping.
With this fix, we check for additional data before returning
kIncompleteInput.
If this lands, I will upload the test image to the bots.
Also adding an invalid image test to CodexTest.
BUG=skia:
Review URL: https://codereview.chromium.org/1273853004
We are also changing the wbmp to use SkSwizzler. This
will allow us to take advantage of the sampling routines
that are being implemented in SkSwizzler.
The image in this upload came from:
https://commons.wikimedia.org/wiki/File:Android_robot.png
It is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
BUG=skia:
Review URL: https://codereview.chromium.org/1254483004
Prior to this CL, if a client wanted to decode scanlines, they had to
create an SkCodec in order to get an SkScanlineDecoder. This introduces
complications if input data is not easily shared between the two
objects.
Instead, add methods to SkScanlineDecoder for creating a new one from
input data, and remove the creation functions from SkCodec.
Update DM and tests.
Review URL: https://codereview.chromium.org/1267583002
This allows codecs that support subsets natively (i.e. WEBP) to do so.
Add a field on SkCodec::Options representing the subset.
Add a method on SkCodec to find a valid subset which approximately
matches a desired subset.
Implement subset decodes in SkWebpCodec.
Add a test in DM for decoding subsets.
Notice that we only start on even boundaries. This is due to the
way libwebp's API works. SkWEBPImageDecoder does not take this into
account, which results in visual artifacts.
FIXME: Subsets with scaling are not pixel identical, but close. (This
may be fine, though - they are not perceptually different. We'll just
need to mark another set of images in gold as valid, once
https://skbug.com/4038 is fixed, so we can tests scaled webp without
generating new images on each run.)
Review URL: https://codereview.chromium.org/1240143002
Make getScanlineDecoder return a new object each time, which is
owned by the caller, and independent from any existing scanline
decoders and the SkCodec itself.
Since the SkCodec already contains the entire state machine, and it
is used by the scanline decoders, simply create a new SkCodec which
is now owned by the scanline decoder.
Move code that cleans up after using a scanline decoder into its
destructor
One side effect is that creating the first scanline decoder requires
a duplication of the stream and re-reading the header. (With some
more complexity/changes, we could pass the state machine to the
scanline decoder and make the SkCodec recreate its own state machine
instead.) The typical client of the scanline decoder (region decoder)
uses an SkMemoryStream, so the duplication is cheap, although we
should consider the extra time to reread the header/recreate the state
machine. (If/when we use the scanline decoder for other purposes,
where the stream may not be cheaply duplicated, we should consider
passing the state machine.)
One (intended) result of this change is that a client can create a
new scanline decoder in a new thread, and decode different pieces of
the image simultaneously.
In SkPngCodec::decodePalette, use fBitDepth rather than a parameter.
Review URL: https://codereview.chromium.org/1230033004
SkImageGenerator makes some assumptions that are not necessarily valid
for SkCodec. For example, SkCodec does not assume that it can always be
rewound.
We also have an ongoing question of what an SkCodec should report as
its default settings (i.e. the return from getInfo). It makes sense for
an SkCodec to report that its pixels are unpremultiplied, if that is
the case for the underlying data, but if a client of SkImageGenerator
uses the default settings (as many do), they will receive
unpremultiplied pixels which cannot (currently) be drawn with Skia. We
may ultimately decide to revisit SkCodec reporting an SkImageInfo, but
I have left it unchanged for now.
Import features of SkImageGenerator used by SkCodec into SkCodec.
I have left SkImageGenerator unchanged for now, but it no longer needs
Result or Options. This will require changes to Chromium.
Manually handle the lifetime of fScanlineDecoder, so SkScanlineDecoder.h
can include SkCodec.h (where Result is), and SkCodec.h does not need
to include it (to delete fScanlineDecoder).
In many places, make the following simple changes:
- Now include SkScanlineDecoder.h, which is no longer included by
SkCodec.h
- Use the enums in SkCodec, rather than SkImageGenerator
- Stop including SkImageGenerator.h where no longer needed
Review URL: https://codereview.chromium.org/1220733013
the bottom of the image. In our code before this patch,
this would result in cleanup code in onFinish() never being
called.
We can allow subclasses to take ownership of the
SkScanlineDecoder in order to make sure that it is
finished/deleted before deleting the decode manager.
BUG=skia:
Review URL: https://codereview.chromium.org/1212593003
Based on SkImageDecoder_libwebp.
TODO:
Support YUV? (Longer term - may influence our API for SkImageGenerator)
BUG=skia:3257
Review URL: https://codereview.chromium.org/1044433002
Enables basic decoding for jpegs
Includes rewinding
565, YUV, and Jpeg encoding are not yet implemented
BUG=skia:3257
Review URL: https://codereview.chromium.org/1076923002
We may want to enable swizzles to 565
for images that are encoded in a format
similar to 565, however, we do not want
to take images that decode naturally to
kN32 and then convert them to 565.
***Enable swizzles to kIndex_8. For images
encoded in a color table format, we suggest
that they be decoded to kIndex_8. When we
decode, we only allow conversion to kIndex_8
if it matches the suggested color type (except
wbmp which seems good as is).
***Modify dm to test images that decode to
kIndex_8.
BUG=skia:3257
BUG=skia:3440
Review URL: https://codereview.chromium.org/1055743003
SkCodec::NewFromStream claims to delete the passed in SkStream on
failure. This allows the caller to pass an SkStream to the function
and not worry about deleting it depending on the return value.
Most of our SkCodecs did not honor this contract though. Update them
to delete the stream on failure. Further, update SkCodec::NewFromStream
to delete the stream if it did not match any subclass, and delete the
SkCodec if we decided to return NULL because it was too big.
Add a test which tests streams which represent the beginnings of
supported format types but do not contain enough data to create an
SkCodec. The interesting part of the test is when we run it on ASAN,
which will report that we leaked something without the other changes.
BUG=skia:3257
Review URL: https://codereview.chromium.org/1058873006
This mirrors the behavior in onGetPixels, and allows the implementation
to share code for handling calls to rewindIfNeeded.
This also fixes a bug where getScanlineDecoder was calling
rewindIfNeeded and treating the result as a bool.
In SkPngCodec, factor out the code to call rewindIfNeeded, and call it
in both onGetPixels and onGetScanlineDecoder.
Update the test to include testing the scanline decoder. Rename "gen"
to "codec" now that it must be an SkCodec.
BUG=skia:3257
Depends on https://codereview.chromium.org/1048423003/ (DIFFERENT ISSUE).
Review URL: https://codereview.chromium.org/1050893002
Separate out the code for reading the header, and use it to reinitialize
fPng_ptr and fInfo_ptr after a rewind.
Use common code to clean up fPng_ptr and fInfo_ptr, and set them to
NULL and treat them as NULL as appropriate.
Update the test to expect SkPngCodec to succeed.
BUG=skia:3257
Review URL: https://codereview.chromium.org/1048423003
