ios - 快速从 UIImage 中找到独特的颜色？

Question

我是IOS开发新手。我已经尝试使用以下代码从 UIImage 获取独特的颜色，但它不起作用。我的图片大小是 360x480。

    let data = CGBitmapContextGetData(context)
    var dataType = UnsafePointer<UInt8>(data)
    var rgb: RGB = (red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0)

    var RedOffSet: UInt8 = 0xE0
    var GreenOffSet: UInt8 = 0xF0
    var BlueOffSet: UInt8 = 0xE0


    var RGBHistogram = [Int](count: 1024, repeatedValue: 0)
    var Top10Colors = [UInt](count: 10, repeatedValue: 0)
    let size: Int = 4 * pixelsWide * pixelsHigh
    var dtIndex = 0


    while(true)
    {
        if(dtIndex < (size - 4)){

            //let alpha   = dataType[0]

            let red     = (dataType[dtIndex + 1]) & RedOffSet
            let green   = (dataType[dtIndex + 2]) & GreenOffSet
            let blue    = (dataType[dtIndex + 3]) & BlueOffSet

            let index = red << 2 | green >> 1 | blue >> 5
            let i: Int = Int(index)
            RGBHistogram[i] += 1
            //dataType += 4
            dtIndex += 1
        }
        else {

            print("Histogramm Created and Exited from Loop Here")
            break;
        }
    }

    //find the Top 10 Colors from Histogramm
    var prevMax = 0
    var max = 0
    var maxJ = 0

    for var indexI in 0 ..< 10 {
        max = 0
        for var indexJ in 0 ..< 1024 {

            if indexI != 0 {

                if (RGBHistogram[indexJ] > max) && (RGBHistogram[indexJ] < prevMax) {
                    max = RGBHistogram[indexJ]
                    maxJ = indexJ
                }
            }
            else {

                if RGBHistogram[indexJ] > max {
                    max = RGBHistogram[indexJ]
                    maxJ = indexJ
                }
            }
        }
        Top10Colors[indexI] = UInt(maxJ)
        prevMax = RGBHistogram[maxJ]
    }

    //Change the Top 10 Cors to its RGB

    for(var index = 0; index < 10; index += 1) {

        let red     = (Top10Colors[index] >> 2) & UInt(RedOffSet)
        let green   = (Top10Colors[index] << 1) & UInt(GreenOffSet)
        let blue    = (Top10Colors[index] << 5) & UInt(BlueOffSet)

        rgb.red = CGFloat(red)
        rgb.green = CGFloat(green)
        rgb.blue = CGFloat(blue)

        cpUniqueColorsList.append(UIColor(red: rgb.red, green: rgb.green, blue: rgb.blue, alpha: 1.0))
    }

使用这段代码，我只能从任何图像中获得 2 种颜色，而不是所有独特的颜色，所以请帮助我解决这个问题。

我已经尝试使用 C++ 编写相同的代码，并且运行良好。

提前致谢分享

Answer 1

UIColor 基于 0..<1.0 的组件值，而不是 0..<256。将每个组件除以 255.0，您应该会得到更好的结果。另请注意，您的哈希算法完全消除了红色 (0xff & 0xe0 << 2) = 0因为该数学将作为 UInt8 完成。