Core Image drawing corruption

Question

I have written two custom Core Image metal kernels which I'm using to produce a CIImage (by chaining several filters). I'm drawing the output image in a simple view and whatever I use (CIImage, NSImage, CGImageRef), the image appears corrupted on screen, like some sort of graphics corruption (I've tried on two different machines with different systems). However if I add a simple step to write the image to disk from the CIImage then read it from disk and draw it in that very same view, then all is fine and the image appears correctly. What could possibly be happening here?

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Posted by

tclementdev

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Can you please upload some screenshots to show what "corrupted" means? Thanks!

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FrankSchlegel
@FrankSchlegel here's a screen recording, top view is drawing the image in drawRect(), bottom view is assigning the image to the layer contents. The bottom view display what I expect. http://tclementdev.com/coreimage_metal_test.mov

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tclementdev
Hmm, this is really hard to debug without seeing the actual filters. But if I would need to guess, I'd say the implementation of the ROI callback (passed when calling the CIKernel) is wrong. I can also recommend using a MTKView for displaying a CIImage instead of using Core Graphics. There is a sample from Apple showing how to do that.

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FrankSchlegel

Answer 1

I've done some further experiments: if I set the CGImage (obtained from the CIImage) directly onto the contents property of the layer of my view, then it works and display fine. But if I implement drawRect() and draw the CGImage into the CGContext using CGContextDrawImage() then it appears corrupted. How weird is that?

Posted by

tclementdev

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Answer 2

For anyone at Apple seeing this, I filed FB12608056 with sample code and screen recording.

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tclementdev

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Core Image drawing corruption

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