ebook-viewer: Transparent PNG renders strangely in dark mode viewer

Bug #1903423 reported by ownedbycats
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
calibre
Undecided
Unassigned

Bug Description

See screenshot. Will attach the exported image in a comment.

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ownedbycats (ownedbycats) wrote :
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ownedbycats (ownedbycats) wrote :

One of the semi-transparent PNGs in this ePub.

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ownedbycats (ownedbycats) wrote :

(Also, disregard my desktop wallpaper. I thought it was funny.)

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Kovid Goyal (kovid) wrote : Re: calibre bug 1903423

Nothing can be done about that. That PNG image is designed to render
against a light background. There is no reasonable way for the viewer to
know that.

 status wontfix

Changed in calibre:
status: New → Won't Fix
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ownedbycats (ownedbycats) wrote :

I find it a bit odd that even though the image frame is grey, the transparency still shows as black. Is that some limitation of Qt?

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Kovid Goyal (kovid) wrote :

its not Qt, put the image in a html file with black background and view
it in a browser.

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ownedbycats (ownedbycats) wrote :

I'm talking about the light grey part surrounding the image. Why does the transparency turn black instead of light grey?

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Kovid Goyal (kovid) wrote :

Oh you mean in the view image popup, i thought you meant in the viewer itself.

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Kovid Goyal (kovid) wrote :

It will be because Qt has to pick some color to use when rendering the transparent pixels in the image. It presumably chooses the default background color, which is white in light mode and black in dark mode The image viewer does not blend the image with gray, the gray is there to improve color perception in the image by surrounding it with a neutral color.

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Kovid Goyal (kovid) wrote : Fixed in master

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased

Changed in calibre:
status: Won't Fix → Fix Released
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