Perhaps call NSRectFillUsingOperation(rect, NSCompositeClear) before
drawing each rectangle?
On Jun 8, 2010, at 5:32 AM, Matej Bukovinski wrote:
* PGP Bad Signature, Signed by an unverified key
Hi,
In a cocoa application that I'm developing I have a custom NSView
subclass that I use as an overlay view for annotating a WebView. The
overlay view draws semi-trasparent rectangles in its drawRect:
method for DOM elements that were selected by the user.
Since the fill color for the drawn rectangles is semi-transparent,
the pixel values get added up when a smaller rectangle is drawn over
a larger one (here's an example http://cl.ly/4fecb8fac0abff6ef6ac ,
as you can see the smaller rectangle has a darker background because
of the larger rectangle, that was drawn first). This is especially
problematic if the rectangles are of different colors, since color
mixing occurs.
I would like to prevent this sort of behavior by somehow "erasing"
the content that was perviously drawn (i.e., making the background
transparent again) before drawing with a new element. Does anyone
have an idea how to achieve this?
Thank you for your time.
Best regards,
Matej
* Matej Bukovinski <ma...@bukovinski.com>
* Issuer: The USERTRUST Network - Unverified
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