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Starred by 6 users
Status: New
Area: Bitmap
Priority: Medium
Type: Defect

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Prescaling images loses subpixel precision in translation
Project Member Reported by, Jul 24 2013 Back to list
What steps will reproduce the problem?
1. Draw a bitmap with a non-trivial scale and a fractional translation

What is the expected output? What do you see instead?

The fractional translation should persist through to the per-scanline bilerp code.  Instead, we remove the scale factor from the matrix after scaling, causing us to think that the matrix is translation-only.  

Unfortunately, for translation-only matrices, we round the translation amounts to the nearest integer.

Need to have a discussion with the right people about why translations are quantized in these cases, and what I should do about it.
Project Member Comment 1 by, May 29 2014

new animated sample to show subpixel translate bug with high quality scaling



Review URL:

git-svn-id: 2bbb7eff-a529-9590-31e7-b0007b416f81

Thu May 29 22:01:08 2014 +0000
M	gyp/SampleApp.gyp
A	samplecode/SampleSubpixelTranslate.cpp
Project Member Comment 2 by, May 30 2014
Status: Started
Project Member Comment 3 by, Oct 13 2014
Labels: Area-Bitmap
Project Member Comment 4 by, Sep 5 2015
Project Member Comment 5 by, Mar 2 2016
Status: New
Confirmed that the example mentioned above still shows the whole pixel jumps described above. However, whole pixel jumps may be desirable in scrolling and zooming applications. Does this bug still have legs?
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