[cairo] Is Cairo able to fit my needs?

Jürgen info at innova-studios.com
Thu Oct 4 00:41:24 PDT 2007

Hi there carl,

when cairo doesnt have bitwise logical operators, how is cairo then able
to display postscript images? i have several postscript images on my
harddisk that use chained objects. that means you have e.g. a black square
and inside of it another smaller black square. when you chain them it
looks like a white square in a black square. (i can draw you an image to
make it visible to you if you want me to)

kind regards juergen

> -----Ursprüngliche Nachricht-----
> Von: Carl Worth [mailto:cworth at cworth.org]
> Gesendet: Mittwoch, 03. Oktober 2007 23:38
> An: Innova-Studios - Juergen Ladstaetter
> Cc: cairo at cairographics.org
> Betreff: Re: [cairo] Is Cairo able to fit my needs?
> On Wed, 3 Oct 2007 22:01:32 +0200, "Innova-Studios - Juergen Ladstaetter"
> wrote:
>> Ad 2) doesn’t that function set the whole graphic to that color?
> No. cairo_fill just fills the current path, (just like the equivalent
> operation in PostScript).
>> Ad 3) normally when painting two things over each other, a logical
> function
>> "COPY" is used. For displaying postscript there are also other functions
>> needed.
>> A small list of functions:
>> wxAND                 src AND dst
>> wxAND_INVERT          (NOT src) AND dst
>> wxAND_REVERSE         src AND (NOT dst)
> ...
> OK, if you want bitwise logical operators then you won't find them in
> cairo. Many cairo output targets, (such as PostScript!), don't have
> any notion of "bits" so such operations are not well-defined at all.
> Cairo does have various operators, but they are the Porter/Duff
> compositing operators, not bitwise arithmetic operators.
> I hope that helps.
> -Carl

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