On 15 Mar 2009, at 5:29 AM, Jean-Daniel Dupas wrote:
Note that if you want to get a revert effect, you can obtains it
drawing white rect with the Quart "Difference Blend Mode".
http://developer.apple.com/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_images/dq_images.html
CGContextRef ctxt = [[NSGraphicsContext currentContext]
graphicsPort];
CGContextSetBlendMode(ctxt, kCGBlendModeDifference);
CGContextSetGrayFillColor(ctxt, 1, 1);
CGContextFillRect(ctxt, NSRectToCGRect(aRect));
With a minor change, this worked perfectly - many thanks to both
people who responded. I am simply unaware of a lot of the API here so
hadn't looked at these functions.
PK
--
Dr Philip Kime
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