[cairo] Image rendering help?
britten at caris.com
Thu Oct 2 09:01:37 PDT 2008
Ian Britten wrote:
> Hi all,
> I was wondering if someone knowledgeable could take a bit of a
> look at the attached (cairomm) test I'm playing with?
[ snip ]
> For the VIA_PATTERN case:
> - (sigh) It doesn't seem to work, even though it seems to be the
> same as my SURFACE case (to me, at least). Can anyone point
> out what's wrong?
Ok, I've made a bit of progress, but I still can't seem to
understand what it's doing, nor how to get what I want.
If I change my VIA_PATTERN case to this:
then my image draws in the upper-left corner. :)
- I don't understand what the get_matrix()/set_matrix() is doing
or why it's necessary. In my mind, I'd think that the default
transformation on the Pattern would be Identity, and when I set
the Pattern on the Context, it would add the Patterns
transformation to the current transformation of the Context,
which would basically be a NOOP in this case. Obviously it
doesn't work that way, and I don't fully understand what's
- I still can't figure out how to change where the image is being
drawn. I've tried adding translate() calls to my matrix,
and/or to my Context (Both before and after setting the Pattern
on it), I've tried adding move_to() calls, and am running out
- To try to get the Image to fill my Surface, I tried adding
a scale() call to the tmpMatrix before setting it on the
pattern. However, my image just disappears then :(
Shouldn't a call like
cairo_matrix_scale(&tmpMatrix, 2, 2);
result in my image drawing at twice its size?
- If I set a rotation on my Surface, then the vector path I'm
drawing is correctly rotated, but my image still appears
unrotated (upright), in the upper-left corner. Does a Pattern
not rotate with a Surface?
[ BTW - I'm using Cairo 1.6.4, just in case it's a bug ]
Am I maybe going about this the wrong way?
Any help/explanation would be _most_ appreciated!
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