ios - vImageMatrixMultiply_ARGB8888ToPlanar8 在构建 Release模式 iOS 应用程序时不起作用

Question

我正在开发图像处理应用程序并尝试使用 vImage。它工作得很好，并在 Debug模式下得到正确的结果。但是，它总是返回黑色图像或在 Release模式下引发错误。

官方已经试过了example当我在 Release模式下构建它时，它也会得到一个黑色图像。

func uiImageToBuffer(image: UIImage) -> vImage_Buffer? {
    guard let cgImage = image.cgImage,
          var format = cgImageFormat(of: image)
    else { return nil }

    var buffer = vImage_Buffer()
    let error = vImageBuffer_InitWithCGImage(&buffer, &format, nil, cgImage, vImage_Flags(kvImageNoFlags))
    if error == kvImageNoError {
        return buffer
    } else {
        return nil
    }
}


func grayBuffer(_ buffer: vImage_Buffer) -> vImage_Buffer {
    var _buffer = buffer
    var destinationBuffer = vImage_Buffer()
    vImageBuffer_Init(&destinationBuffer, buffer.height, buffer.width, 8, vImage_Flags(kvImageNoFlags))

    let redCoefficient: Float = 0.2126
    let greenCoefficient: Float = 0.7152
    let blueCoefficient: Float = 0.0722

    let divisor = Float(0x1000)

    var coefficientsMatrix = [
        Int16(redCoefficient * divisor),
        Int16(greenCoefficient * divisor),
        Int16(blueCoefficient * divisor)
    ]

    var preBias: Int16 = 0
    let postBias: Int32 = 0

    vImageMatrixMultiply_ARGB8888ToPlanar8(&_buffer, &destinationBuffer,
                                           &coefficientsMatrix, 0x1000, &preBias, postBias, vImage_Flags(kvImageNoFlags))

    return destinationBuffer
}

func main() {
    guard let imageBuffer = uiImageToBuffer(image: image),
          var grayBuffer = grayBuffer(buffer) 
    else { return }

    var monoFormat = vImage_CGImageFormat(bitsPerComponent: 8, bitsPerPixel: 8,
                                  colorSpace: Unmanaged.passRetained(CGColorSpaceCreateDeviceGray()),
                                  bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue),
                                  version: 0, decode: nil, renderingIntent: .defaultIntent)

    let cgImage = vImageCreateCGImageFromBuffer(&grayBuffer, &monoFormat, nil, nil, vImage_Flags(kvImageNoFlags), nil)
    if let cgImage = cgImage {
        imageView.image = UIImage(cgImage: cgImage.takeRetainedValue())
    }
    free(imageBuffer.data)
    free(grayBuffer.data)
}

Answer 1

预偏置应该是一个包含四个元素的向量。试试这个:

let preBias: [Int16] = [0, 0, 0, 0]
let postBias: Int32 = 0

vImageMatrixMultiply_ARGB8888ToPlanar8(&_buffer, 
                                       destinationBuffer,
                                       &coefficientsMatrix, 
                                       0x1000, 
                                       preBias, 
                                       postBias, 
                                       vImage_Flags(kvImageNoFlags))