Erase a rect of an UIImageView - iphone

Question

I want to know, how can I erase a custom rect (with, for example, an UIView in IB or something else) of an UIImageView in order to display an other UIImageView positioned underneath.
I didn't manage to do it using some response in the forum...

Answer 1

This will clear a rect in an image:
- (UIImage *)clearRect:(CGRect)rect inImage:(UIImage *)image {
if (UIGraphicsBeginImageContextWithOptions != NULL)
UIGraphicsBeginImageContextWithOptions([image size], NO, 0.0);
else
UIGraphicsBeginImageContext([image size]);
CGContextRef context = UIGraphicsGetCurrentContext();
[image drawInRect:CGRectMake(0.0, 0.0, [image size].width, [image size].height)];
CGContextClearRect(context, rect);
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Just load your image and clear the rects before assigning it to the image view:
UIImage *image = [UIImage imageNamed:#"Image.png"];
UIImage *maskedImage = [self clearRect:CGRectMake(10.0, 10.0, 50.0, 50.0) inImage:image];
[imageView setImage:maskedImage];

Answer 2

probably not the best solution but you can do the other way and take the 4 parts around the rect separately and combine them afterwards without the inner rect. You would repeat this as long as you have rect's to crop out.

Answer 3

You cannot clear the UIImageView itself because this just draws the UIImage. So you have erase the rect in the UIImage. Create a bitmap context, draw the image into it. Erase the part you want to "see through" with CGContextClearRect. When create a new new image from the bitmap context.