将 UIImage 转换为单色 1 位 bmp 图像 Swift 5.1

Question

PS：我想要的结果是 [Bool] 格式。即，0 表示背景，1 表示除背景以外的任何颜色。

我有一个每像素 32 位的 UIImage。如何制作二值图像（即 1bit .bmp 图像）

我正在使用下面的代码：但它全部为零

  public extension UIImage {

        func pixelData() -> [UInt8]? {
                let size = self.size
                let dataSize = size.width * size.height
                var pixelData = [UInt8](repeating: 0, count: Int(dataSize))
                let colorSpace = CGColorSpaceCreateDeviceRGB()
                let context = CGContext(data: &pixelData,
                                        width: Int(size.width),
                                        height: Int(size.height),
                                        bitsPerComponent: 1,
                                        bytesPerRow:Int(size.width),
                                        space: colorSpace,
                                        bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)
                guard let cgImage = self.cgImage else { return nil }
                context?.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))

                return pixelData
            }
}

Answer 1

我已经创建了一个可能有点牵强的解决方案。

首先，我创建了一个像素结构，描述了一个像素代表什么。

struct Pixel {

    var r: Float
    var g: Float
    var b: Float
    var a: Float
    var row: Int
    var col: Int

    init(r: UInt8, g: UInt8, b: UInt8, a: UInt8, row: Int, col: Int) {
        self.r = Float(r)
        self.g = Float(g)
        self.b = Float(b)
        self.a = Float(a)
        self.row = row
        self.col = col
    }

    var color: UIColor {
        return UIColor(
            red: CGFloat(r/255.0), 
            green: CGFloat(g/255.0), 
            blue: CGFloat(b/255.0), 
            alpha: CGFloat(a/255.0)
        )
    }

    var description: String {
        return "\(r), \(g), \(b), \(a)"
    }

}

然后我创建了一个 UIImage 扩展。

extension UIImage {

    var pixelData: [Pixel] {
        let bmp = self.cgImage!.dataProvider!.data
        var data: UnsafePointer<UInt8> = CFDataGetBytePtr(bmp)
        var r, g, b, a: UInt8
        var pixels = [Pixel]()

        for row in 0 ..< Int(self.size.width) {
            for col in 0 ..< Int(self.size.height) {
                r = data.pointee
                data = data.advanced(by: 1)
                g = data.pointee
                data = data.advanced(by: 1)
                b = data.pointee
                data = data.advanced(by: 1)
                a = data.pointee
                data = data.advanced(by: 1)
                pixels.append(Pixel(r: r, g: g, b: b, a: a, row: row, col: col))
            }
        }
        return pixels
    }

    var monochrome: UIImage? {
        let context = CIContext(options: nil)
//        let currentFilter = CIFilter(name: "CIPhotoEffectNoir")
        let currentFilter = CIFilter(name: "CIColorMonochrome")
        currentFilter?.setValue(CIImage(image: self), forKey: kCIInputImageKey)
        guard let output = currentFilter?.outputImage, 
              let cgImage = context.createCGImage(output, from: output.extent) else {
            print("Failed to create output image")
            return nil
        }
        return UIImage(cgImage: cgImage, scale: scale, orientation: imageOrientation)
    }

}

我确实创建了单色滤镜，您可以看到注释代码，您可以使用它来创建灰度滤镜。

之后，我所要做的就是对其进行测试和解析：

let image = UIImage(named: "Test2")!

let grayScale: [Bool] = image.pixelData.map {
    var white: CGFloat = 0
    var alpha: CGFloat = 0

    $0.color.getWhite(&white, alpha: &alpha)
    return white > 0.5
}

var trues  = 0
var falses = 0

grayScale.forEach {
    if $0 {
        trues += 1
    } else {
        falses += 1
    }
}

最后一步也可以转换为扩展。希望这会有所帮助！