iOS - Saving only a part of a UIView to PNG - ios

Question

I am using the following code to convert the contents of a UIView to a PNG image:
UIGraphicsBeginImageContext(myView.bounds.size);
[myView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This works fine. If the UIView is 500 pixels high, and I'd like to generate two images (one of the top half and one of the bottom half), how would I go about doing this?
Any help would be greatly appreciated.

Answer 1

There are a few ways you could do this. One way is to draw it into one big image, then make two sub-images:
static UIImage *halfOfImage(UIImage *fullImage, CGFloat yOffset) {
// Pass yOffset == 0 for the top half.
// Pass yOffset == 0.5 for the bottom half.
CGImageRef cgImage = fullImage.CGImage;
size_t width = CGImageGetWidth(cgImage);
size_t height = CGImageGetHeight(cgImage);
CGRect rect = CGRectMake(0, height * yOffset, width, height * 0.5f);
CGImageRef cgSubImage = CGImageCreateWithImageInRect(cgImage, rect);
UIImage *subImage = [UIImage imageWithCGImage:cgSubImage scale:fullImage.scale
orientation:fullImage.imageOrientation];
CGImageRelease(cgSubImage);
return subImage;
}
...
UIGraphicsBeginImageContext(myView.bounds.size);
[myView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImage *topHalfImage = halfOfImage(viewImage, 0);
UIImage *bottomHalfImage = halfOfImage(viewImage, 0.5f);