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This question is as much an iOS question than an Xcode 4.01 question, perhaps more. I apologize if you think this is the wrong list and will shut up if told so.
My iOS app runs fine on the simulator, but crashes on the device.
In fact "crash" is perhaps incorrect. The symptoms are:
- the crash happens when stepping over this code line: [self drawInRect:destRect]; where
"self" is a UIImage
- the app display all go away, showing the springboard.
- the Xcode button is still enabled, suggesting that my app is still running.
- the debugger console doesn't report anything *at all*: no error, no exception, nothing
- the debug navigator is empty and only shows "Process Running"
- the pause/continue button is in its "continue" state (right pointing arrow), just as it was before stepping over. pressing it does nothing
- pressing my app icon on the device's multitasking bar restarts it from scratch.
- pressing Xcode's stop button seems to kill the app, but without any additional output in the debugger console
The code is from a small category I wrote on UIImage to draw thumbnails for images. It's quite straightforward and shown entirely below.
My suspicion is that this problem is memory related, as the image I am trying to scale down here is 6622x9361 pixels in a 6 MB JPEG file.
But none of my AppDelegate related routines is called
How can I confirm this? Is there any debugging technique I can use?
Jean-Denis
- (UIImage *) copyScaledTo:(CGFloat) newScale
{
UIImage *resultImage;
NSDate *chronoStart = [NSDate
date];
if (NO) {
resultImage = [[UIImage
alloc] initWithCGImage:self.CGImage
scale:1.0/newScale
orientation:self.imageOrientation];
// this doesn't work: initWithCGImage:scale:orientation: doesn't resample. It only change the bounds
} else {
CGRect sourceRect =
CGRectZero;
sourceRect.size=
self.size;
CGRect destRect = (CGRect){{0.0,
0.0}, {sourceRect.size.width * newScale, sourceRect.size.height * newScale}};
// Create a low res image representation of the source image to display before the TiledJPEGView
// renders its content.
UIGraphicsBeginImageContext(destRect.size);
CGContextRef context =
UIGraphicsGetCurrentContext();
// First fill the background with white.
CGContextSetRGBFillColor(context,
1.0,1.0,1.0,1.0);
CGContextFillRect(context,destRect);
CGContextSaveGState(context);
// Flip the context so that the image is rendered
// right side up.
if (false) {
// necessary for PDF, not for images
CGContextTranslateCTM(context,
0.0, destRect.size.height);
CGContextScaleCTM(context,
1.0, -1.0);
}
// Scale the context so that the image is rendered
// at the correct size for the zoom level.
// CGContextScaleCTM(context, newScale, newScale);
// in fact, its incorrect to do that, as scaling is already handled by sizing of destRect
// we must do either, but not both
[self drawInRect:destRect];
CGContextRestoreGState(context);
resultImage = [UIGraphicsGetImageFromCurrentImageContext()
retain];
UIGraphicsEndImageContext();
}
NSDate *chronoStop = [NSDate
date];
NSTimeInterval chrono = [chronoStop
timeIntervalSinceDate:chronoStart];
NSLog(@"Thumbnail for %@ image scaled to %.1f%% at %@ in %.2f ms",
NSStringFromCGSize(self.size), newScale*100,
NSStringFromCGSize(resultImage.size), chrono*1000);
return resultImage;
}
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