Iphone How to make context background transparent?

Question

CALayer *sublayer = [CALayer layer]; /*sublayer.backgroundColor = [UIColor blueColor].CGColor; sublayer.shadowOffset = CGSizeMake(0, 3); sublayer.shadowRadius = 5.0; sublayer.shadowColor = [UIColor blackColor].CGColor; sublayer.shadowOpacity = 0.8;*/ sublayer.frame = CGRectMake(30, 100, 256, 256); sublayer.contents = (id)[[UIImage imageNamed:@"moon.png"] CGImage]; [self.view.layer addSublayer:sublayer]; //self.view.backgroundColor = [UIColor blackColor];  //add moon mask UIGraphicsBeginImageContextWithOptions(CGSizeMake(400, 400), YES, 1); CGContextRef contextRef = UIGraphicsGetCurrentContext(); CGContextClearRect(contextRef, CGRectMake(0, 0, 400, 400)); CGContextSetRGBFillColor(contextRef, 1, 1, 1, 0.8); CGContextSetRGBStrokeColor(contextRef, 0, 0, 0, 0.5); CGRect ellipse = CGRectMake(50, 50, 128, 128); CGContextAddEllipseInRect(contextRef, ellipse); CGContextFillEllipseInRect(contextRef, ellipse);  CALayer* sublayer2 = [CALayer layer]; sublayer2.frame = CGRectMake(30, 100, 256, 256); sublayer2.backgroundColor = [UIColor clearColor].CGColor; sublayer2.contents = (id)[UIGraphicsGetImageFromCurrentImageContext() CGImage]; [self.view.layer addSublayer:sublayer2]; 

This is the code i have written so far. First i make layer with moon image. Then i add second layer with custom drawing that should cover part of the moon. However contextRef renders its background black, so when i put second layer, first is invisible. Is there any way i can solve this? Better yet is there a better way to make custom drawing programatically and add it to layer?

Answer 1

UIGraphicsBeginImageContextWithOptions(CGSizeMake(400, 400), NO, 1); 

Setting this argument to NO solves my problem.