Could you please post the relevent code you are using? The "fill a transparent arc on the mask" part sounds incorrect, you need to clear it using CAIRO_OPERATOR_CLEAR.<br>example python code:<br>------<br>import cairo<br>
<br>canvas = cairo.ImageSurface(cairo.FORMAT_ARGB32,320,240)<br>ctx = cairo.Context(canvas)<br><br>#fill with blue<br>ctx.set_source_rgb(0,0,1)<br>ctx.paint()<br><br>#Construct Mask<br>maskSurface = cairo.ImageSurface(cairo.FORMAT_ARGB32,320,240)<br>
ctxM = cairo.Context(maskSurface)<br>ctxM.set_source_rgba(1,1,1,1)<br>ctxM.paint()<br><br>#knock out rectangle <br>ctxM.rectangle(50,50,100,100)<br>ctxM.set_source_rgba(0,0,0,1)<br>ctxM.set_operator(cairo.OPERATOR_CLEAR)<br>
ctxM.fill()<br><br>maskPattern = cairo.SurfacePattern(maskSurface)<br><br>debug = False<br>if debug:<br> #show mask<br> ctx.set_source(maskPattern)<br> ctx.paint()<br>else:<br> #use mask<br> ctx.set_source_rgb(0,1,0)<br>
ctx.mask(maskPattern)<br><br>canvas.write_to_png("out.png")<br>------<br><br><div class="gmail_quote">On Mon, May 26, 2008 at 12:36 PM, Ricky Wood <<a href="mailto:rickywoodster@yahoo.co.uk">rickywoodster@yahoo.co.uk</a>> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I'm new to cairo and probably missing some obvious concept, please can someone enlighten me with this problem:<br>
<br>Basically, I have a surface with some shapes already drawn onto it. I now want to paint every part of the surface a single colour except a circle, i.e. leave the contents of the surface, where the circle lies, undisturbed.<br>
<br>The approach I took was:<br><br>- create a mask<br>- paint the mask totally opaque<br>- fill a transparent arc on the mask<br>- set the colour on the source<br>- cairo_mask<br><br>I thought the source colour would be transferred to the destination, leaving the circle masked.<br>
<br>Where have I gone wrong, or is there a better approach?<br><br>TIA.<br><div class="WgoR0d"><br><p>
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