mixChannels()理解

基于下面两个例子的理解：

示例一：4通道图像分割

 1 #include<opencv2/opencv.hpp>
 2 using namespace cv;
 3 
 4 int main()
 5 {
 6     Mat bgra(500, 500, CV_8UC4, Scalar(255, 255, 0, 255));
 7     Mat bgr(bgra.rows, bgra.cols, CV_8UC3);
 8     Mat alpha(bgra.rows, bgra.cols, CV_8UC1);
 9 
10     Mat out[] = { bgr, alpha };
11 
12     int from_to[] = { 0, 2, 1, 1, 2, 0, 3, 3 };
13     mixChannels(&bgra, 1, out, 2, from_to, 4);
14 
15     imshow("bgra", bgra);
16     imshow("bgr", bgr);
17     waitKey(0);
18     return 0;
19 }

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示例二：HSV通道获取

 1 #include<opencv2/opencv.hpp>
 2 
 3 using namespace cv;
 4 
 5 int main()
 6 {
 7     Mat src, hsv, dst;
 8     src = imread("D:\\hsv.jpg");
 9     if (src.empty())
10     {
11         printf("can not load image \n");
12         return -1;
13     }
14     namedWindow("input", WINDOW_AUTOSIZE);
15     imshow("input", src);
16     cvtColor(src, hsv, COLOR_BGR2HSV);
17     dst.create(hsv.size(), hsv.depth());
18     //分离Hue/色相通道
19     int ch[] = { 0, 0 };
20     mixChannels(&hsv, 1, &dst, 1, ch, 1);
21     imshow("H channel", dst);
22     //分离Saturation/饱和度通道
23     int ch1[] = { 1, 0 };
24     mixChannels(&hsv, 1, &dst, 1, ch1, 1);
25     imshow("S channel", dst);
26     //分离Value/色调通道
27     int ch2[] = { 2, 0 };
28     mixChannels(&hsv, 1, &dst, 1, ch2, 1);
29     imshow("V channel", dst);
30 
31     waitKey(0);
32     return 0;
33 }