OpenCVSharp4 卡通效果

            Mat lena = Cv2.ImRead("lena.jpg");

            // 卡通化
            Mat imgBF = new Mat();
            Cv2.BilateralFilter(lena, imgBF, 9, 150, 150);

            // 丢弃一些颜色
            Mat result = imgBF / 25;
            result = result * 25;
            // 转换到float，为后续乘法做准备
            Mat resultF = new Mat();
            result.ConvertTo(resultF, MatType.CV_32FC3);


            // 中值过滤，去噪点
            Mat imgMedian = new Mat();
            Cv2.MedianBlur(lena, imgMedian, 7);

            // canny 检测边缘
            Mat imgCanny = new Mat();
            Cv2.Canny(imgMedian, imgCanny, 50, 150);

            // 膨胀边缘
            Mat kernel = Cv2.GetStructuringElement(MorphShapes.Rect, new Size(2, 2));
            Cv2.Dilate(imgCanny, imgCanny, kernel);
            // 反转，变成黑色，保证边缘是黑色
            imgCanny = 255 - imgCanny;

            Mat imgCannyF = new Mat();
            imgCanny.ConvertTo(imgCannyF, MatType.CV_32FC3);
            imgCannyF /= 255;// 取值限制到0~1，为后续乘法做准备
            // 模糊平滑边缘线
            Cv2.Blur(imgCannyF, imgCannyF, new Size(5, 5));
            Mat imgCanny3C = new Mat();
            Mat[] imgCanny3Cs = { imgCannyF, imgCannyF, imgCannyF };
            Cv2.Merge(imgCanny3Cs, imgCanny3C); // 合并图

            Cv2.Multiply(resultF, imgCanny3C, resultF);

            resultF.ConvertTo(result, MatType.CV_8UC3);

            Cv2.ImShow("lena", lena);
            Cv2.ImShow("imgBF", imgBF);
            Cv2.ImShow("imgCanny", imgCanny);
            Cv2.ImShow("result", result);

            Cv2.WaitKey();

lesson5-1.jpg

采取方案为

• 去噪之后采用canny得到边缘

        //
        // 摘要:
        //     Finds edges in an image using Canny algorithm.
        //
        // 参数:
        //   src:
        //     Single-channel 8-bit input image
        //
        //   edges:
        //     The output edge map. It will have the same size and the same type as image
        //
        //   threshold1:
        //     The first threshold for the hysteresis procedure
        //
        //   threshold2:
        //     The second threshold for the hysteresis procedure
        //
        //   apertureSize:
        //     Aperture size for the Sobel operator [By default this is ApertureSize.Size3]
        //
        //   L2gradient:
        //     Indicates, whether the more accurate L2 norm should be used to compute the image
        //     gradient magnitude (true), or a faster default L1 norm is enough (false). [By
        //     default this is false]
        public static void Canny(InputArray src, OutputArray edges, double threshold1, double threshold2, int apertureSize = 3, bool L2gradient = false);

• 使用双边滤波函数BilateralFilter得到卡通化的底片
  双边滤波器可以很好的保存图像边缘细节而滤除掉低频分量的噪音，但是双边滤波器的效率不是太高，花费的时间相较于其他滤波器而言也比较长。

        //
        // 摘要:
        //     Applies bilateral filter to the image
        //
        // 参数:
        //   src:
        //     The source 8-bit or floating-point, 1-channel or 3-channel image
        //
        //   dst:
        //     The destination image; will have the same size and the same type as src
        //
        //   d:
        //     The diameter of each pixel neighborhood, that is used during filtering. If it
        //     is non-positive, it's computed from sigmaSpace
        //
        //   sigmaColor:
        //     Filter sigma in the color space. Larger value of the parameter means that farther
        //     colors within the pixel neighborhood will be mixed together, resulting in larger
        //     areas of semi-equal color
        //
        //   sigmaSpace:
        //     Filter sigma in the coordinate space. Larger value of the parameter means that
        //     farther pixels will influence each other (as long as their colors are close enough;
        //     see sigmaColor). Then d>0 , it specifies the neighborhood size regardless of
        //     sigmaSpace, otherwise d is proportional to sigmaSpace
        //
        //   borderType:
        public static void BilateralFilter(InputArray src, OutputArray dst, int d, double sigmaColor, double sigmaSpace, BorderTypes borderType = BorderTypes.Reflect101);

对于简单的滤波而言，可以将两个sigma值设置成相同的值，如果值<10，则对滤波器影响很小，如果值>150则会对滤波器产生较大的影响，会使图片看起来像卡通。

• 两张图叠加

           Cv2.Multiply(resultF, imgCanny3C, resultF);