Drawing a PNG Image Into a Graphics Context for Blending Mode Manipulation

Question

I need to draw a series of PNGs into a CGContext so I can blend them together:

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSe         


        

Answer 1

You don't need to be using UIImageViews. Instead, bracket your drawing between calls to UIGraphicsBeginImageContext and UIGraphicsEndImageContext.

For example (code not tried):

UIImage* uiimage = [UIImage imageNamed:@"image-name.png"];
UIImage* uiimage2 = [UIImage imageNamed:@"other-image-name.png"];

CGSize size = uiimage.size; 

UIGraphicsBeginImageContext(size);

[uiimage drawAtPoint:CGPointZero blendMode:kCGBlendModeOverlay alpha:1.0];
[uiimage2 drawAtPoint:CGPointZero blendMode:kCGBlendModeOverlay alpha:1.0];

UIImage* blendedImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

If you want to use CG calls, call:

CGContextRef context = UIGraphicsGetCurrentContext();

to get the context ref.