On Thursday 20 May 2004 12:01, Melchior FRANZ wrote:
> BTW: this is my little transparency trick: in my fgfs.mp library file I
> have this:
>
>    color foreground, transparent;
>    background:=black;
>    transparent:=white;
>    white:=255/256white;
>    foreground:=white;
>
> which lets white actually be written as 254/254/254 ... white enough (who
> needs true white, anyway), and transparent areas are 255/255/255. Note that
> 1/2a is the same as (1/2)a or .5a, and not 1/(2a).
>
>           ***
>
> now I can "draw foo withcolor transparent"
>
>           ***
>
> and later, in my Makefile I have lines like these:
>
>
>    foo.rgb: foo.mp Makefile
>            mpost foo.mp
>            convert -density 1024x1024 foo.1 -transparent white -resize
> 256x256 sgi:foo.rgb

One can also use Gimp to turn a color to alpha (Filters->Colors->Color to 
Alpha...). When doing this, the shades of the color becomes "shades" of 
alpha. For antialiased edges this works very well. Downside is of course that 
it is much more work :-(

-- 
Roy Vegard Ovesen


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