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Re: CG vs QuickDraw

On Sun, 10 Jun 2007 10:52:07 -0700, Philip Aker <email@hidden> wrote:


Trying to draw a 1 point non-antialiased line. Filed a bug: -- "Works as expected". Sorry to be so forthright, but I think that's sub-standard.

What do you mean? What is it that doesn't work as you expect? All you need to remember are 2 rules:
CG like virtally all graphics systems use pixel boundaries for positioning, and CGContextStrokePath/CGContextStrokeRect centers the line on the path you specified.

So if you do CGContextMoveToPoint/CGContextAddLineToPoint with integer values, and have an odd line width it will of course look blurry, because you specified half the line to be drawn the pixels on either side of the path (which, as said, runs on the pixel boundary.

If you want the 1-pixel-wide line to not span several pixels, you simply add 0.5, so
CGContextMoveToPoint(ctx, 10.5, 4); CGContextAddLineToPoint(ctx, 10.5, 24);

If it is diagonal lines you don't want antialiasing on, there is always CGContextSetShouldAntialias.

- Anders
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References: 
 >CG vs QuickDraw (From: Ingemar Ragnemalm <email@hidden>)
 >Re: CG vs QuickDraw (From: Philip Aker <email@hidden>)



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