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Re: . alpha channel circles RGB overlapping

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In article <227f97c0-c204-4442-ba27-93402277cbde@googlegroups.com>, 
jodun@mail.com says...

> Hi  GHOSTSCRIPT gurus !

Ths is a PostScript group, not a Ghostscript group. PostScript is a 
language, Ghostscript is an interpreter for that language. There are 
other PostScript interpreters.

 
> How to draw overlapping marks
> of different RGB colors
> every mark has half transparency
> 
>             say 
> 
> the famous 3 overlapping/intersecting circles
> a red circle
> a green circle
> a blue
> 
> each circle of 50% opacity/transparency/alphachannelity
> The 3 circles may intersect symmetrically (or not)

If you read the PLRM you will see that PostScript does not support alpha 
channels. There is no support for transparency in PostScript, with a few 
exceptions;

1) Masked images and imagemasks. This involves either 0 or 100% opacity, 
so transparencym but not translucency.

2) overprint. Ths simply doesn't erase underlying marks when drawing new 
ones, so it doesn't do any alpha channel blending either. Also overprint 
is specified to only apply to CMYK colours, so you can't use it with RGB 
colourants.

The figure you describe would most easily be drawn as three circles, 
each of a different colour R, G or B, then the three segments where each 
overlaps would have to be drawn separatly with a different colour, and 
finally the segment where all three overlap would again be drawn as a 
separate operation.


			Ken

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. alpha channel circles RGB overlapping jodun@mail.com - 2015-05-21 12:28 -0700
  Re: . alpha channel circles RGB overlapping ken <ken@spamcop.net> - 2015-05-22 07:55 +0100
    Re: . alpha channel circles RGB overlapping luser- -droog <mijoryx@yahoo.com> - 2015-06-12 19:10 -0700

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