[cairo] Hi all and a couple questions...
jamagallon at ono.com
Thu Oct 30 02:24:07 PDT 2008
Hi to everyone...
I have just discovered cairo, and it's far far better than plain gdk.
I use it fot a portable application between Linux and Win, and
works flawlessly both in Xp and Vista.
Thanks for the good work!!.
Everything is working fine, but a thing.
I can't get a way to paint grayscale images without converting them
to 24/32 bits.
I'm writing a little app to do image processing that works with gray
images from a Bassler camera, and don't want to waste memory converting
them to RGB. But cairo does not have a plain 'gray image' surface
type, just an 'alpha channel' type. I have tried with several
source/fill colors, operators, etc but can't find the right combo.
What I suspect I should do is to paint in white filtered by my grayscale
alpha to get to the destination surface. But I can't get it right.
My code is basicly like this:
// Clear the region to get some base color to draw on top
// set the source alpha, image() is A8
// set the source color
The above code paints the image in negative.
What should I use as base color/alpha to fill the surface, and what
operator to paint the image the right way ?
And other question is: How could I disable image interpolation in
cairo_paint() ? I want to zoom my image and see big square pixels, not
the (fancy, btw) interpolation that cairo does by default ?
Thanks in advance for your time.
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2009.0 (Cooker) for i586
Linux 2.6.25-jam18 (gcc 4.3.1 20080626 (GCC) #1 SMP
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