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POPerfromance Issues In CGContextDrawLayerAtPoint in iOS 4.0
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copied!<p>I'm having some performance issues calling CGContextDrawLayerAtPoint in iOS 4 that didn't seem to exist in previous version of the OS.</p> <p>I'm copying a layer obtained from a bitmap context created with CGBitmapContextCreate to my view's context during a drawRect call. The view and the bitmap are the same size. </p> <p>The bitmap was created with:</p> <pre><code>CGBitmapContextCreate(NULL, width, height, 8, width * 4, genericRGBSpace, kCGBitmapByteOrder32Host | kCGImageAlphaNoneSkipFirst); </code></pre> <p>Instruments in indicating I'm spending more time in CGContextDrawLayerAtPoint than I was on devices running OS 3.2. In fact the stack trace indicates the following stack trace taking a higher percentage of time:</p> <pre><code>argb32_sample_argb32 argb32_image_mark argb32_image ripl_Mark ripl_BltImage RIPLayerBltImage ripc_RenderImage ripc_DrawLayer CGContextDelegateDrawlayer CGContextDrawLayerAtPoint </code></pre> <p>whereas the same code running under 3.2 shows</p> <pre><code>argb32_image_mark_rgb32 argb32_image ripl_Mark ripl_BltImage ripc_RenderImage ripc_DrawLayer CGContextDelegateDrawLayer CGContextDrawLayerAtPoint </code></pre> <p>with a much lower percentage of time. I'm not sure exactly why argb32_sample_argb32 is being called on iOS 4 and what it's doing - sampling the existing data into a new buffer? I'm not sure why this would be necessary. The view and the bitmap are the same size and no scaling has been performed. </p> <p>Any insight into this would be appreciated.</p>

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