Draw selected areas of a UIImage

Question

I have a UIImage containing an image with a whole bunch of smaller pictures on the image (essentially an image strip containing sprites). I'd like to draw a single sprite onto an area of my UIView.

I can't seem to find a way draw only part of the UIImage onto the view. Is there a method that does this?

Answer 1

Yep, you sure can with Quartz.

There is a tutorial here that shows you how to take a UIImage and mask a part of it.

http://iphonedevelopertips.com/cocoa/how-to-mask-an-image.html

Here is the code from that page (incase it goes down for some reason)

- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

    CGImageRef maskRef = maskImage.CGImage; 

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
     CGImageGetHeight(maskRef),
     CGImageGetBitsPerComponent(maskRef),
     CGImageGetBitsPerPixel(maskRef),
     CGImageGetBytesPerRow(maskRef),
     CGImageGetDataProvider(maskRef), NULL, false);

    CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
    return [UIImage imageWithCGImage:masked];

}

Answer 2

I think you may be looking for CGImageCreateWithImageInRect(). You can get a CGImage from a UIImage with the property of the same name.