On 5/18/05, Chris Cannam <[EMAIL PROTECTED]> wrote:
> On Wednesday 18 May 2005 16:03, Alexandre Prokoudine wrote:
> > Excuse me my ignorance, but what is the problem about"true
> > transparency" in current RG's icons?
> 
> XPM allows you to specify that a pixel has a colour, or that it is
> transparent, but not both (i.e. it can't be partially transparent).
> PNG doesn't have this limitation.
> 
> Imagine you want to draw an anti-aliased black shape on a coloured
> background.  Anti-aliasing works by blending the pixels around the
> edges into the background to various degrees to make them appear to be
> "partly in" the shape.  To do it right, therefore, you need to know the
> colour of the background -- if you draw a light grey pixel on a dark
> red background, it doesn't blend in at all.  XPM doesn't allow you to
> do this, because coloured pixels cannot also be transparent.  So you
> have to make your icons to fit a particular colour background (in our
> case a light grey).
> 
> This is one reason why Rosegarden's icons look crappy if you change your
> KDE theme to one with a dark background -- the anti-aliasing
> practically glows, because the icons were made for a light background.
> Of course there's more to it than that -- you can't just plonk a dark
> icon on a dark background either -- but that's the technological part
> of the problem at least.

Ah, I see now. Thank you for the explanation. 

I've dealed only a couple of times with XPM without digging into it
deeply, though it was actually about turning XPMs to PNGs (for
Scribus). Which reminds me about one thing: is it possible to use a
PNG image as custom cursor instead of a B/W XPM image in X11/X.org?

Alexandre


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