CGImageRef orignImage = [UIImage imageNamed:@"image"].CGImage;
CGContextDrawImage(contextRef, CGRectMake...(0, 0, 320, 200), orignImage);
CGImageRef rectImage = CGImageCreateWithImageInRect(orignImage, CGRectMake...(300, 400, 800, 400));
CGContextDrawImage(contextRef, CGRectMake(0, 220, 320, 200), rectImage);...:@"image2"].CGImage;
//设置填充
[[UIColor redColor] setFill];
CGContextFillRect(contextRef, CGRectMake...(0, 0, 320, 200), mask);
CGContextDrawImage(contextRef, CGRectMake(0, 0, 320, 200), orignImage);