155 Views 3 Replies
      Latest reply on Aug 20, 2019 8:22 PM by KMT
      skajam66 Level 1 Level 1 (0 points)
      skajam66 Aug 19, 2019 12:58 AM

        I am unable to get an image that was originally created via a CIFilter to display in IB on on a simulator.  Display on a device is fine.

         

        Here is how I am rendering the image:

                if let f = constructFilter(radius: radius, value: sliderView.value.hsba.brightness), let foi = f.outputImage {
            circleView.image = UIImage(ciImage: foi)
        }

         

        And here is how I consruct the filter (the 'value' input parameter is always 1.0):

            private func constructFilter(radius: CGFloat, value: CGFloat) -> CIFilter? {
        guard let cs = CGColorSpace.init(name: CGColorSpace.extendedSRGB) else { return nil }
        
        return CIFilter(name: "CIHueSaturationValueGradient", parameters: [
            "inputColorSpace" : cs,
            "inputDither" : 0,
            "inputRadius" : radius,
            "inputSoftness" : 0,
            "inputValue" : value])
    }

         

        The specific color space doesn't change the behaviour. This also fails:

                return CIFilter(name: "CIHueSaturationValueGradient", parameters: [
            "inputColorSpace" : CGColorSpaceCreateDeviceRGB(),
            "inputDither" : 0,
            "inputRadius" : radius,
            "inputSoftness" : 0,
            "inputValue" : value])

         

        Of course, if I generate the image from a resource it works just fine on device, IB and simulator.

         

        Poking around in the debugger, I notice that extracting png data from the UIImage returns nil when the image has been created from CIFilter  - which could explain why IB and simulator fail to display anything

         

        Any thoughts would be welcome.

         

        Regards,

        ac

        • Re: Cannot get a CIFilter originated image to display in IB or simulator
          FrankSchlegel Level 3 Level 3 (120 points)
          FrankSchlegel Aug 20, 2019 11:51 AM (in response to skajam66)

          When you create a UIImage from a CIImage (UIImage(ciImage: foi)), the filter is not actually applied yet. Only when the UIImage is used somewhere, the GPU would process your filter chain. And from my experience this is not very reliable in all scenarios.

           

          What you can do instead is to explicitly render the CIImage into a CGImage and continue with that:

           

          let context = CIContext() // ideally you only create that once and re-use it
if let outputCGImage = context.createCGImage(image: foi, from: foi.extent) {
    circleView.image = UIImage(cgImage: outputCGImage)
}
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            • Re: Cannot get a CIFilter originated image to display in IB or simulator
              skajam66 Level 1 Level 1 (0 points)
              skajam66 Aug 20, 2019 8:15 PM (in response to FrankSchlegel)

              Frank,

               

              Thanks you for your response.  I have resolved the issue following along with your advice thus:

               

                      if let f = constructFilter(radius: radius, brightness: sliderView.value.hsba.brightness), let foi = f.outputImage {
            #if TARGET_INTERFACE_BUILDER
            let context = CIContext()
            if let outputCGImage = context.createCGImage(foi, from: foi.extent) {
                circleView.image = UIImage(cgImage: outputCGImage)
            }
            #else
            circleView.image = UIImage(ciImage: foi)
            #endif
        }

               

              I am curious as to the underlying issue here and how IB rendering differs from device rendering. Maybe it is GPU related?

               

              If you have any insights on this I would appreciate heraing them.

               

              Regards,

              ac