Why properties method of CIImage returns nil

Question

I'm developing an application using coreImage framework.I created a CIImage from UIImage.

CIImage *image = [CIImage imageWithCGImage:self.canvasImage.CGImage];

here self.canvasImage is a UIImage,I debug it and object image is being created by compiler with some memory.

i'm creating a NSDictionary object returned by properties method using following code.

NSDictionary *opts  =[image properties] ;

here my opts object is being assign with nil value.

i searched it but didn't found the solution,why properties method is returning nil value?

Answer 1

I was having this same problem. Turns out the properties dictionary is only non nil if you use the imageWithData: or imageWithContentsOfURL: to create the CIImage.

It's not documented well at all. Check out WWDC 2013 session 509.