Convert bitmap to PNG or JPG using Objective C

Anyone 开发者_开发问答knows how to convert a bitmap to PNG or JPG using Objective C assuming I have

CGImageRef imageRef;

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UIImage *myImage = [UIImage imageWithCGImage:imageRef];
NSData *pngData = UIImagePNGRepresentation(myImage);
NSData *jpgData = UIImageJPEGRepresentation(myImage);