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POWhy is drawInContext so slow here?
 

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  1. POWhy is drawInContext so slow here?
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    <p>I'm using the QuartzImage class in one of the demo projects and what I'm was trying to achieve was a simple frame display unit that basically draws an image (320x480) every 1/10th of sec. So my "frame rate" should be 10 frames per sec. </p> <p>In the QuartzImage demo class, there is a drawInContext method and in this method, it's basically drawing a CGImageRef using the CGContextDrawImage(), I measured the time it took to finish complete and it's taking on average around ~200ms.</p> <pre><code>2011-03-24 11:12:33.350 QuartzDemo[3159:207] drawInContext took 0.19105 secs -(void)drawInContext:(CGContextRef)context { CFAbsoluteTime start = CFAbsoluteTimeGetCurrent(); CGRect imageRect; imageRect.origin = CGPointMake(0.0, 0.0); imageRect.size = CGSizeMake(320.0f, 480.0f); CGContextDrawImage(context, imageRect, image); CFAbsoluteTime end = CFAbsoluteTimeGetCurrent(); NSLog(@"drawInContext took %2.5f secs", end - start); } </code></pre> <p>Can anyone explain why it's taking that long and if there is any other way of improving the performance? 200ms just seems much more longer than it should have taken.</p> <p><strong>UPDATES</strong> I tried @Brad-Larson's suggestion but not seeing a lot of performance improvement. </p> <p>So the updated version is I got my own class </p> <pre><code>@interface FDisplay : UIView { CALayer *imgFrame; NSInteger frameNum; } end </code></pre> <p>So in my Class implementation </p> <pre><code>- (id)initWithFrame:(CGRect)frame { ............ frameNum = 0; NSString *file = [NSString stringWithFormat:@"frame%d",frameNum]; UIImage *img = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:file ofType:@"jpg"]]; imgFrame = [CALayer layer]; CGFloat nativeWidth = CGImageGetWidth(img.CGImage); CGFloat nativeHeight = CGImageGetHeight(img.CGImage); CGRect startFrame = CGRectMake(0.0, 0.0, nativeWidth, nativeHeight); imgFrame.contents = (id)img.CGImage; imgFrame.frame = startFrame; CALayer *l = [self layer]; [l addSublayer:imgFrame]; } </code></pre> <p>I have a NSTimer going at 0.1f calling my refresh method</p> <pre><code>NSString *file = [NSString stringWithFormat:@"frame%d",frameNum]; UIImage *img = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:file ofType:@"jpg"]]; frameNum++; if (frameNum&gt;100) frameNum = 0; [CATransaction begin]; [CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions]; [imgFrame setContents:(id)img.CGImage]; [CATransaction commit]; end = CFAbsoluteTimeGetCurrent(); NSLog(@"(%d)refresh took %2.5f secs", [[self subviews] count],end - start); </code></pre> <p>I think I got everything right but the frame rate is still way low, </p> <pre><code>refresh took 0.15960 secs </code></pre>
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