白平衡，灰度世界算法（C# EmguCv）

//白平衡算法，灰度世界算法 preset色溫

enum WB_PRESET
    {
        //自動白平衡 
        AUTO,
        //陰天 7500k 
        CLOUDY,
        //日光 6500k  
        DAYLIGHT,
        //白熱光 5000k  
        INCANDESCENCE,
        //日光燈 4400k 
        FLUORESCENT,
        //鎢絲燈 2800k  
        TUNGSTEN,
    };

void GrayWorld(Image<Bgr, Byte> img, WB_PRESET preset)
        {
            int avgR = 0, avgG = 0, avgB = 0;
            int sumR = 0, sumG = 0, sumB = 0;
            for (int h = 0; h < img.Height; ++h)
            {
                for (int w = 0; w < img.Width; ++w)
                {
                    sumB += img.Data[h, w, 0];
                    sumG += img.Data[h, w, 1];
                    sumR += img.Data[h, w, 2];
                }
            }
            int size = img.Height * img.Width;
            avgB = sumB / size;
            avgG = sumG / size;
            avgR = sumR / size;
            //double k = (avgB + avgG + avgR) / 3;
            double k = 0.299 * avgR + 0.587 * avgG + 0.114 * avgB;

            switch (preset)
            {
                case WB_PRESET.AUTO:
                    avgR = (sumR / size);
                    avgG = (sumG / size);
                    avgB = (sumB / size);
                    break;
                case WB_PRESET.CLOUDY:
                    avgR = (int)(sumR * 1.953125 / size);
                    avgG = (int)(sumG * 1.0390625 / size);
                    avgB = (int)(sumB / size);
                    break;
                case WB_PRESET.DAYLIGHT:
                    avgR = (int)(sumR * 1.2734375 / size);
                    avgG = (int)(sumG / size);
                    avgB = (int)(sumB * 1.0625 / size);
                    break;
                case WB_PRESET.INCANDESCENCE:
                    avgR = (int)(sumR * 1.2890625 / size);
                    avgG = (int)(sumG / size);
                    avgB = (int)(sumB * 1.0625 / size);
                    break;
                case WB_PRESET.FLUORESCENT:
                    avgR = (int)(sumR * 1.1875 / size);
                    avgG = (int)(sumG / size);
                    avgB = (int)(sumB * 1.3125 / size);
                    break;
                case WB_PRESET.TUNGSTEN:
                    avgR = (int)(sumR / size);
                    avgG = (int)(sumG * 1.0078125 / size);
                    avgB = (int)(sumB * 1.28125 / size);
                    break;
                default:
                    break;
            }

            double kr = k / avgR;
            double kg = k / avgG;
            double kb = k / avgB;
            double newB, newG, newR;
            for (int h = 0; h < img.Height; ++h)
            {
                for (int w = 0; w < img.Width; ++w)
                {
                    newB = img.Data[h, w, 0] * kb;
                    newG = img.Data[h, w, 1] * kg;
                    newR = img.Data[h, w, 2] * kr;

                    img.Data[h, w, 0] = (byte)(newB > 255 ? 255 : newB);
                    img.Data[h, w, 1] = (byte)(newG > 255 ? 255 : newG);
                    img.Data[h, w, 2] = (byte)(newR > 255 ? 255 : newR);
                }
            }

        }