GPUImage2 : HarrisCornerDetector not calling callback

问题

I have an odd problem implementing corner detection using GPUImage.

I'm trying to use the filter template from Brad's download as a starting point, but although I can generate a composite view of the image and the corner points (as single white pixels), when I try to add in the crosshair generator, the callback function is never called.

In my simplified example, I have an output view configured as RenderView and videoCamera defined as Camera?

    do {
        videoCamera = try Camera(sessionPreset:AVCaptureSessionPreset640x480, location:.backFacing)
        videoCamera!.runBenchmark = true
    } catch {
        videoCamera = nil
        print("Couldn't initialize camera with error: \(error)")
    }

    let filter = HarrisCornerDetector()

    let crosshairGenerator = CrosshairGenerator(size: Size(width: 480, height: 640))

    filter.cornersDetectedCallback = { corners in
        crosshairGenerator.renderCrosshairs(corners)
    }
    videoCamera! --> filter

    let blendFilter = AlphaBlend()
    videoCamera! --> blendFilter --> renderView
    //crosshairGenerator --> blendFilter    // INPUT 1: if I add this line, the callback never happens
    filter --> blendFilter                  // INPUT 2: with this input to blendFilter, the callback is good

As shown, the callback function is called as expected, and I see little white dots in the output.

If I remove comments to enable INPUT 1, and comment out INPUT 2, the display shows the camera only, and the corner detection callback is never called.

The sample project that Brad provides works on my device, so I know there's no hardware or iOS issue!

Any thoughts?

回答1:

You forgot to input your crosshair width

crosshairGenerator.crosshairWidth = 15.0

and there is no threshold that you declared

回答2:

Make the Harris-detector object an instance property.

来源：https://stackoverflow.com/questions/43980462/gpuimage2-harriscornerdetector-not-calling-callback

标签

ios

swift

gpuimage