Erase a rect of an UIImageView

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 开发者_JS百科to do it using some response in the forum...

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];

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.

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.