1.8.2 - view - png - tRNS transparency - viewing issues

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user0
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1.8.2 - view - png - tRNS transparency - viewing issues

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XnViewMP 1.8.2 64bit
Windows11 (24H2), display resolution 3840x2160, win scaling 150%


Viewer/Browser(Preview) - png - tRNS transparency
png transparency via tRNS chunk (aka 'cheap alpha') turns out to be a bit more complicated

viewer_view_png_transparency.png
test_img_png_transparency.zip

Issue A
test images 3, 6 are rendered w/o transparency (Viewer/Browser thumbnails, preview)

Issue B
state of transparency controls (enabled/disabled) needs to be adjusted (in Viewer > View menu)

Issue C
the following transparency controls do not work when some antialiasing filters are applied (eg zoom>100%):
- Use transparency index
- Use alpha channel
- Show alpha


ref
https://www.w3.org/TR/png-3/#11transinfo
http://www.libpng.org/pub/png/book/chap ... ch08.div.5
http://www.libpng.org/pub/png/spec/1.2/ ... C.Anc-trns




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