ios - 将 UIImage 转换为 8-Gray 类型的像素缓冲区

Question

我可以将 a 转换UIImage为 ARGB CVPixelBuffer，但现在我正在尝试将 a 转换UIImage为灰度缓冲区。自从代码通过以来，我以为我已经拥有了它，但是 coreML 模型抱怨说：

“错误域 = com.apple.CoreML 代码 = 1 “图像不是 8 灰色类型，而是不受支持 (40)”

CGContext这是我到目前为止的灰度：

public func pixelBufferGray(width: Int, height: Int) -> CVPixelBuffer? {

        var pixelBuffer : CVPixelBuffer?
        let attributes = [kCVPixelBufferCGImageCompatibilityKey: kCFBooleanTrue, kCVPixelBufferCGBitmapContextCompatibilityKey: kCFBooleanTrue]

        let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(width), Int(height), kCVPixelFormatType_8IndexedGray_WhiteIsZero, attributes as CFDictionary, &pixelBuffer)

        guard status == kCVReturnSuccess, let imageBuffer = pixelBuffer else {
            return nil
        }

        CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

        let imageData =  CVPixelBufferGetBaseAddress(imageBuffer)

        guard let context = CGContext(data: imageData, width: Int(width), height:Int(height),
                                      bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(imageBuffer),
                                      space: CGColorSpaceCreateDeviceGray(),
                                      bitmapInfo: CGImageAlphaInfo.none.rawValue) else {
                                        return nil
        }

        context.translateBy(x: 0, y: CGFloat(height))
        context.scaleBy(x: 1, y: -1)

        UIGraphicsPushContext(context)
        self.draw(in: CGRect(x:0, y:0, width: width, height: height) )
        UIGraphicsPopContext()
        CVPixelBufferUnlockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

        return imageBuffer

    }

任何帮助将不胜感激

Answer 1

即使图像被称为灰度，正确的像素格式是：kCVPixelFormatType_OneComponent8

---

希望这个完整的代码片段能帮助别人：

public func pixelBufferGray(width: Int, height: Int) -> CVPixelBuffer? {

        var pixelBuffer : CVPixelBuffer?
        let attributes = [kCVPixelBufferCGImageCompatibilityKey: kCFBooleanTrue, kCVPixelBufferCGBitmapContextCompatibilityKey: kCFBooleanTrue]

        let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(width), Int(height), kCVPixelFormatType_OneComponent8, attributes as CFDictionary, &pixelBuffer)

        guard status == kCVReturnSuccess, let imageBuffer = pixelBuffer else {
            return nil
        }

        CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

        let imageData =  CVPixelBufferGetBaseAddress(imageBuffer)

        guard let context = CGContext(data: imageData, width: Int(width), height:Int(height),
                                      bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(imageBuffer),
                                      space: CGColorSpaceCreateDeviceGray(),
                                      bitmapInfo: CGImageAlphaInfo.none.rawValue) else {
                                        return nil
        }

        context.translateBy(x: 0, y: CGFloat(height))
        context.scaleBy(x: 1, y: -1)

        UIGraphicsPushContext(context)
        self.draw(in: CGRect(x:0, y:0, width: width, height: height) )
        UIGraphicsPopContext()
        CVPixelBufferUnlockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))

        return imageBuffer

    }