CIFilter filterWithCVPixelBuffer returning nil in iOS

Question

I am trying to create a CIFilter using filterWithCVPixelBuffer and it is returning nil. This is what I'm trying to do:

CFDictionaryRef options = CMCopyDictionaryOfAttachments(nil, photo.pixelBuffer, kCMAttachmentMode_ShouldPropagate);
CIFilter * ciFilter = [CIFilter filterWithCVPixelBuffer:photo.pixelBuffer properties:(__bridge NSDictionary*)options options:nil];

photo is an instance of AVCapturePhoto given to the delegate. I am using iOS 12 and running the code on iPhone7.

Answer 1

The problem was in the properties NSDictionary. I should have simply passed photo.metadata. So the function call would look like:

CIFilter * ciFilter = [CIFilter filterWithCVPixelBuffer:photo.pixelBuffer properties:photo.metedata options:nil];

Of course, you can pass an NSDictionary containing the desired CIRAWFilterOption(s) .

Answer 2

I think I found the answer in the documentation in the header file:

Returns a CIFilter that will in turn return a properly processed CIImage as "outputImage".

Note that when using this initializer, you should pass in a CVPixelBufferRef with one of the following Raw pixel format types kCVPixelFormatType_14Bayer_GRBG, kCVPixelFormatType_14Bayer_RGGB, kCVPixelFormatType_14Bayer_BGGR, kCVPixelFormatType_14Bayer_GBRG as well as the root properties attachment from the CMSampleBufferRef .

So I guess this method should be used when you have a CMSampleBuffer and is not feasible when coming from a AVCapturePhoto .