[Libreoffice-bugs] [Bug 135910] Transparent objects either possess outlines when none are defined or are completely opaque, depending on export PNG options

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=135910

--- Comment #10 from mwtjunkmail at gmail.com ---
(In reply to Mike Kaganski from comment #9)
> The problem is that now, when the painting of objects happens on a clear
> transparent vdev, painting the object (e.g. rectangle in case of attachment
> 164477 [details]), happening in two stages (RGB separately, alpha
> separately), only sees white background while drawing RGB. AA makes the
> painting to blend with the background on edges, which results in the borders
> of the shape to become light (and semi-transparent, but the unintended
> *color* change happens anyway).
> 
> I suppose that it should instead somehow see that the pixels it blends with
> are completely transparent, and then do not change color, and only apply AA
> to transparency. But I don't yet have an idea how to perform that in out
> weird separated (RGB / Alpha) graphics.
> 
> Thorsten, quikee, Lubos: possibly you have some ideas?

Exports using the TIFF format (both whole slide and as a selection) do not
exhibit any of the problems this or my previous bug listed (but I need PNG
files).

Perhaps model the PNG export after however TIFF handles it?

--- Comment #11 from mwtjunkmail at gmail.com ---
(In reply to Mike Kaganski from comment #9)
> The problem is that now, when the painting of objects happens on a clear
> transparent vdev, painting the object (e.g. rectangle in case of attachment
> 164477 [details]), happening in two stages (RGB separately, alpha
> separately), only sees white background while drawing RGB. AA makes the
> painting to blend with the background on edges, which results in the borders
> of the shape to become light (and semi-transparent, but the unintended
> *color* change happens anyway).
> 
> I suppose that it should instead somehow see that the pixels it blends with
> are completely transparent, and then do not change color, and only apply AA
> to transparency. But I don't yet have an idea how to perform that in out
> weird separated (RGB / Alpha) graphics.
> 
> Thorsten, quikee, Lubos: possibly you have some ideas?

Exports using the TIFF format (both whole slide and as a selection) do not
exhibit any of the problems this or my previous bug listed (but I need PNG
files).

Perhaps model the PNG export after however TIFF handles it?

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