App crashes when saving picture to library

Question

Hi all, I have a problem with my app when testing it on my iphone. I have a method that combines 4 images in one and saves it to the photo library:

    - (UIImage *)combineImages{
        UIImage *image1 = firstImgView.image;
        UIImage *image2 = secondImgView.image;
        UIImage *image3 = thirdImgView.image;
        UIImage *image4 = fourthImgView.image;

        UIGraphicsBeginImageContext(image1.size);

        [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];
        [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];
        [image3 drawInRect:CGRectMake(0, 0, image3.size.width, image3.size.height)];
        [image4 drawInRect:CGRectMake(0, 0, image4.size.width, image4.size.height)];

        UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();

        return resultingImage;  
    }
//save actual design in photo library
- (void)savePicture{
    UIImage *myImage = [self combineImages];
    UIImageWriteToSavedPhotosAlbum(myImage, self, @selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), self); 
}

//feedback if picture saving was successfull
- (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {  
    NSString *message;  
    NSString *title;  
    if (!error) {  
        title   = NSLocalizedString(@"Image saved", @"");  
       // message = NSLocalizedString(@"Your image was saved", @"");  
    } else {  
        title   = NSLocalizedString(@"Error", @"");  
        message = [error description];  
    }  
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title  
                                                    message:message  
                                                   delegate:nil  
                                          cancelButtonTitle:NSLocalizedString(@"Ok", @"")  
                                          otherButtonTitles:nil];  
    [alert show];  
    [alert release];  
} 

When I want to test it I get the following error: *Program received signal: “EXC_BAD_ACCESS”. Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.) warning: Cancelling call - objc code on the current thread's stack makes this unsafe.*

In the simulator it works fine.

Answer 1

If the images total over 1k x 1k pixels, then my guess is that you ran out of memory on the device. The Simulator has a ton more memory available. Run the memory allocations Instrument on the Simulator build and see how much your images and the compositing operation actually consume, peak.

Answer 2

My guess is that you must retain combined image before passing it to UIImageWriteToSavedPhotosAlbum. Combined image is autoreleased and it can be freed before the actual save is done. Try this:

//save actual design in photo library
- (void)savePicture{
    UIImage *myImage = [self combineImages];
    [myImage retain];
    UIImageWriteToSavedPhotosAlbum(myImage, self, @selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), self); 
}

//feedback if picture saving was successfull
- (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {  
    [image release];
    // ...
}

Answer 3

Found the error... kind of a dumb error. It was that line

 // message = NSLocalizedString(@"Your image was saved", @""); 

I should've not commented it out. Now everything works fine.