Hey,
https://invent.kde.org/graphics/krita/-/blob/master/plugins/impex/tiff/tests/data/quad-jpeg.tif
is the file in question.
What we'd need is to get the bitmap as interleaved, uncompressed YCbCr,
since that's what our rendering engine ingests. Based on how the other
compression formats behave like, it seems that what gets out of libtiff
right now is the raw JPEG-encoded strip.
amyspark
On 21/05/2022 17:21, Kemp Watson wrote:
Not sure about your particular file, but we extract hundreds of thousands of
YCbCr JPEG images from TIFFs every day...
W. Kemp Watson
Objective Pathology Services
Toronto, Canada
http://www.objectivepathology.com
[email protected]
tel. +1 (647) 783-4431
On May 21, 2022, at 3:37 PM, L. E. Segovia via Tiff <[email protected]>
wrote:
Hi all,
Recently one of my colleagues at Krita found an abandoned TIFF in our source
code repository that, to the best of our knowledge, had never been checked into
our test suite.
Turns out, it is a JPEG-compressed, YCbCr TIFF. I've recently added color space
profiles for YCbCr, but when loading this sample inside our app, the output
shows significant corruption as well as misaligned strips.
I've tried the tiff2rgba and rgba2ycbcr tools to generate copies, and can
confirm that:
- Loading YCbCr TIFFs with anything but JPEG compression works.
- Loading RGBA TIFFs with any compression, including JPEG, works.
which leads me to conclude that the expected layout of YCbCr + JPEG doesn't match what it
says on the tin ("Ordering of Component Samples", page 93 of the standard).
Unfortunately, I can't verify my suspicions with libtiff's source code itself, as in all
cases, either the data is already in RGB form or libjpeg-turbo is asked to convert it to
RGB.
Does anyone know what the layout of this kind of data is? Or, alternatively,
where I could start looking?
Best,
amyspark
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