libpng dependency issue

Vincent Povirk madewokherd+8cd9 at
Fri Feb 5 08:54:13 CST 2010

> I was looking in to the overall architectural issues but have not had
> the time to really hack on it recently. As far as I understand, the
> current png support in wine's windowscodecs does not support creation
> of a 32bpp image with transparency, unless I missed some commit
> messages or totally misunderstood our discussions. I believe from my
> reading native does support doing the conversions, saving the alpha
> channel information, applying the masking, etc.

It's supported 32bpp with transparency from the start. The full list
of supported writing formats is here:

GUID_WICPixelFormat32bppBGRA is the format you want, I think.

You probably tried to use a format not on that list, which defaults to
24-bit. I'm not sure what the behavior should be in that case.

> I was working on a patch for winemenubuilder so we would at least have
> that part part done, even if it only spit out 24bpp images without
> transparency but never got very far with it. If I recall correctly,
> the current code parses the raw ico bitmapinfo, passes that to libpng,
> applies the mask and generates the resulting image. I tried a few
> different ways, using WIC to open a stream to the icon that was then
> parsed by the icon decoder feeding the png encoder to generate the
> image. I also tried using the existing parsing system, feeding that to
> the bitmap decoder then the png encoder and never could get it to work
> quite right. With the patch I had, the resulting png image was corrupt
> possibly due to some RGB/BGR issue, I seem to recall Vincent
> mentioning something about that as well.

That's odd. Both WIC and winemenubuilder appear to be using BGR for
32-bit pixel formats and informing libpng of this . I don't know where
you could be getting RGB pixels.

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