Icons, logos, Tango, consistency, the user experience, and our project looks like a 2D champaign flute

Joel Holdsworth joel at airwebreathe.org.uk
Sat Apr 18 14:08:30 CDT 2009

> From: http://www.telegraphics.com.au/svn/icoformat/trunk/dist/README.html
>     "The ICO format has an inherent 1 bit transparency mask (0 =
> opaque, 1 = transparent), called the AND bitmap."
> which is the older format icon. and:
>     "In PNG (Vista) format icons, the alpha channel is simply stored
> as part of the PNG. There is no separate mask."
> http://www.rw-designer.com/windows-xp-icon
> http://www.rw-designer.com/vista-icon
> According to these, you can store the images as PNG in Vista instead
> of BMP+mask, allowing you to preserve the alpha channel. Vista also
> supports 256x256 icon images (according to the information above).
> http://www.axialis.com/tutorials/tutorial-vistaicons.html
> http://msdn.microsoft.com/en-us/library/aa511280.aspx
> Have some more information. From the MDSN article, it appears that
> toolbar images (and other images stored in image lists?) only support
> a 1-bit alpha mask.
> http://msdn.microsoft.com/en-us/magazine/cc546571.aspx
> Has information on the new format. Note that PNG can be used in place
> of DIB image data.
> It shouldn't be too difficult to use something like libpng to handle
> the images and produce a bitmap from it. This would need support on
> the resource compiler side as well.
> IIRC, Wine *does* support AlphaBlending, but it is very slow.
> - Reece

AFAIK - Windows has supported icon transparency since XP - or even
before. In the case of XP, transparency was supported simply through
32-bit bitmaps, which is what I've used in my patch.

This works fine in XP, and you can see it in action, because many icons
have subtle drop-shadows and the like. I believe in that case, the
transparency mask would be unused, or maybe be set as a simple
transparency = (alpha==0) value by the authoring app as an attempt at
backward compatibility. 

32-bit uncompressed (or RLE) works fine for small icons - even up to
48x48, but these days high resolution is becoming more and more common,
and we're seeing icons containing images up to as large as 256x256px.
But in 32-bit uncompressed that's a quater megabyte, which is enough to
make most engineers wince, hence the introduction of PNG!

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