[cairo] Fwd: BUG: CAIRO_FORMAT_ARGB32, image_surface transparency = CAIRO_IMAGE_IS_OPAQUE after write_png()

Guillermo Rodriguez guillerodriguez.dev at gmail.com
Tue Jun 7 09:04:58 UTC 2016

2016-06-07 9:29 GMT+02:00 Lawrence D'Oliveiro <ldo at geek-central.gen.nz>:
> On Tue, 7 Jun 2016 08:19:47 +0930, Adrian Johnson wrote:
>> Cairo analyses image transparency to ensure it uses the most
>> efficient format when writing out images to
>> PNG, PDF, and PS.
> I don’t mind PDF and PostScript, they’re quite complicated formats. But
> I thought the PNG reading/writing capability built into Cairo was
> supposed to be, and I quote, “a toy API”
> <https://www.cairographics.org/manual/cairo-PNG-Support.html>.
> Optimizing out the alpha channel would have to count as an “advanced”
> feature, not a “toy” one, I would have thought.

I guess that describing it as a toy API simply means "not
feature-complete" and/or "no warranties if you use this in your
It does not mean that any advanced features need to be left out, or
that the implementation must be a dumb one.


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