Question

I am trying to take a picture from a camera and overlay the image from a UIButton — which has been moved/rotated/scaled to some place on the screen.

The code below rotates the image properly but does not place it at the proper X,Y coordinates.

- (UIImage*)dumpOverlayViewToImage {
    CGSize imageSize = self.cameraOverlayView.bounds.size;
    UIGraphicsBeginImageContext(imageSize);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(ctx, self.button.frame.origin.x, self.button.frame.origin.y);
    CGContextConcatCTM(ctx, self.button.transform);
    [self.button.imageView.image drawAtPoint:CGPointMake(0,0)];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return viewImage;
}    

Help would be greatly appreciated.

Answer 1

If you are on a device with a retina display, you probably need to take that into account. The easiest way in this case should be to use this instead of UIGraphicsBeginImageContext:

UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);