Multiple Clipped Rects to Create Collage in Core Graphics

Question

I am creating a collage combined with elements from other images. Here is some ASCII art to explain what I am doing:

Given images A, B and C,
AAA, BBB, CCC
AAA,         


        

Answer 1

The upside down image can be corrected by calling the below method :

CGImageRef flip (CGImageRef im) {
CGSize sz = CGSizeMake(CGImageGetWidth(im), CGImageGetHeight(im));
UIGraphicsBeginImageContextWithOptions(sz, NO, 0);
CGContextDrawImage(UIGraphicsGetCurrentContext(),
                   CGRectMake(0, 0, sz.width, sz.height), im);
CGImageRef result = [UIGraphicsGetImageFromCurrentImageContext() CGImage];
UIGraphicsEndImageContext();
return result;

}

Take help from below code as to where u will put this code:

UIGraphicsBeginImageContextWithOptions(CGSizeMake(leftRect.size.width, leftRect.size.height), NO, 0);
CGContextRef con = UIGraphicsGetCurrentContext();
CGContextDrawImage(con, leftRect,flip(leftReference));