UIKIT_EXTERN NSData * __nullable UIImagePNGRepresentation(UIImage * __nonnull image); // return image as PNG. May return nil if image has no CGImageRef or invalid bitmap format UIKIT_EXTERN NSData * __nullable UIImageJPEGRepresentation(UIImage * __nonnull image, CGFloat compressionQuality); // return image as JPEG. May return nil if image has no CGImageRef or invalid bitmap format. compression is 0(most)..1(least)