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POCaching to CGLayer slower than redrawing on iPhone
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copied!<p>I'm in the process of making a simple drawing program for the iPhone. At the moment, touch events add their location to a list which is connected with a bunch of CGContextAddLineToPoint calls which are redrawn in every call to drawRect.</p> <p>I'm running into performance issues at fairly low numbers of lines (they are transparent, though), so I tried drawing everything into a CGLayer. Now, instead of drawing each line every frame, it draws each line only once and draws the CGLayer to the screen every frame.</p> <pre><code> CGContextRef backgroundContext = CGLayerGetContext(pathBuffer); CGContextSetLineWidth(backgroundContext, 2.0); CGContextSetLineCap(backgroundContext, kCGLineCapButt); CGContextSetStrokeColorWithColor(backgroundContext, [pathColor CGColor]); if([[touchPoints objectAtIndex:0] continuesToNextPoint]) { CGContextMoveToPoint(backgroundContext, [[touchPoints objectAtIndex:0] point].x, [[touchPoints objectAtIndex:0] point].y); CGContextAddLineToPoint(backgroundContext, [[touchPoints objectAtIndex:1] point].x, [[touchPoints objectAtIndex:1] point].y); CGContextStrokePath(backgroundContext); } //remove it from touchpoints [touchPoints removeObjectAtIndex:0]; } CGContextRef context = UIGraphicsGetCurrentContext(); CGContextDrawLayerAtPoint(context, CGPointMake(0, 0), pathBuffer); </code></pre> <p>This, if anything, is SLOWER than what I was doing before. Am I doing something wrong? Would I be better served drawing to a UIImage or something? Thanks.</p>

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