swift - CIImageProcessorKernel 示例代码返回全白结果

Question

我尝试使用 https://developer.apple.com/documentation/coreimage/ciimageprocessorkernel 中的示例代码对手机摄像头捕获的图像进行二值化处理。 ，即:

首先将 CIImageProcessorKernel 子类化为:

class ThresholdImageProcessorKernel: CIImageProcessorKernel {
    static let device = MTLCreateSystemDefaultDevice()        
    override class func process(with inputs: [CIImageProcessorInput]?, arguments: [String : Any]?, output: CIImageProcessorOutput) throws {                
        guard            
            let device = device,            
            let commandBuffer = output.metalCommandBuffer,            
            let input = inputs?.first,            
            let sourceTexture = input.metalTexture,            
            let destinationTexture = output.metalTexture,            
            let thresholdValue = arguments?["thresholdValue"] as? Float else  {                
                return        
            }                

        let threshold = MPSImageThresholdBinary(
                device: device,                                                
                thresholdValue: thresholdValue,                                               
                maximumValue: 1.0,                                                
                linearGrayColorTransform: nil)                

        threshold.encode(
            commandBuffer: commandBuffer,                         
            sourceTexture: sourceTexture,                         
            destinationTexture: destinationTexture)    
    }
}

然后将其用作(在开发者页面中有一个拼写错误，在 ThresholdImageProcessorKernel 处缺少一个 r):

    let result = try? ThresholdImageProcessorKernel.apply( 
        withExtent: inputImage.extent,            
        inputs: [inputImage],            
        arguments: ["thresholdValue": 0.25])

结果是全白图像？？

Answer 1

一定要覆盖 outputFormat 和 formatForInput。例如:

override class var outputFormat: CIFormat {
    return kCIFormatBGRA8
}
override class func formatForInput(at input: Int32) -> CIFormat {
    return kCIFormatBGRA8
}