renderInContext not support mask? - ios

Question

I have a camera app to load photo into a device with mask. Everything is OK. When I try to use renderInContext to save the view to an image, I only see the image without any mask.
UIGraphicsBeginImageContext(contentView.bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[contentView.layer renderInContext:context];
UIImage *outImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(outImage, self, #selector(image: didFinishSavingWithError: contextInfo:), context);
I have read some paper from Apple to say that renderInContext don't support mask and composition. I've made some search on the internet to get the information that UIView needed to draw as a context first and then use renderInContext to save the image.
Now my question is what method to do the job? What about drawRect, drawInRect, drawLayer, drawInContent, or other method. Can anyone give me a hint. Thanks a lots.

Answer 1

I started from here: http://chinkisingh.com/2013/03/03/draw-on-iphoneipad-screen-using-bezier-paths-core-graphics-ios-app-development/
I have a UIBezierPath and I wanted to apply a gradient to it and apply to an existing image, see if the following code helps
CGRect r = CGRectMake(0, 0, HEART_SIZE, HEART_SIZE);
UIBezierPath *heart = [Bezier heartShape:r]; //this is only in my case
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
UIColor *darkPink = [UIColor colorWithHue:0.915 saturation:1.000 brightness:0.941 alpha:1.000];
UIColor *lightPink = [UIColor colorWithHue:0.917 saturation:0.647 brightness:1.000 alpha:1.000];
NSArray *gradientColors = [NSArray arrayWithObjects:
(id)darkPink.CGColor,
(id)lightPink.CGColor,
(id)darkPink.CGColor, nil];
CGFloat gradientLocations[] = {0, 0.5, 1};
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)gradientColors, gradientLocations);
CGColorSpaceRelease(colorSpace);
UIGraphicsBeginImageContext(r.size);
heart.lineCapStyle = kCGLineCapRound;
heart.lineWidth = 10.0f;
[[UIColor blackColor] setStroke];
[[UIColor redColor] setFill];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
[heart stroke]; //removed the black stroke around
[heart fill];
CGContextAddPath(context, heart.CGPath);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, CGPointMake(10, 10), CGPointMake(210, 210), kCGGradientDrawsAfterEndLocation); //check that gradient is drawn in the right place
CGGradientRelease(gradient);
UIImage *theRightImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();