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iosavfoundationcore-imagecgaffinetransform

How to use kCIInputTransformKey on iOS

I'm creating a CIFilter for a AVMutableVideoComposition

Since it doesn't support both a filter and layer instructions, I tried to apply the transform I need directly in the filter:

    filter.setValue(transform, forKey: kCIInputTransformKey)

Where transform is a CGAffineTransform

This throws the exception

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key inputTransform.'

Now the doc says

A key for an NSAffineTransform object that specifies a transformation to apply.

But NSAffineTransform does not exist on iOS.

How to use CGAffineTransform or iOS, or what substitute could replace it ?

Solution

  • My solution was to apply directly the transform in the filter.

    This can be done by applying it to the source image.

    request.sourceImage.transformed(by: transform)

    edit: As Frank pointed out; not all filters support transforms!