图像指定坐标点的各通道像素值提取

颜色空间每个像素点由红,蓝,绿三个颜色组成，简单地说每个像素点的颜色是像调色板一样由红,蓝,绿三个颜色调制而成，因此每个像素点由红蓝绿三个像素坐标值-简称为三通道坐标！

使用 cvGet2D(图片， y坐标， x坐标)获取 CvScalar 对象。

输出 CvScalar对象的 val[0],  val[1],  val[2]

CvScalar s = cvGet2D(img, y, x);
printf(" RGB : B=%d, G=%d, R=%d \n" , (int)s.val[0], (int)s.val[1], (int)s.val[2]);

完整程序如下。

#include <ctype.h>
#include <stdlib.h>
#include <cv.h>
#include <highgui.h>

int main(int argc, char** argv)
{
IplImage *img = 0;
IplImage *hsv = 0;

int x = 0;
int y = 0;

int error = 0;

int splitType = -1;
uchar p[3];

if (argc = 4)
{

if (!(img = cvLoadImage(argv[1])))
{
error = 1;
}

if (isdigit(argv[2][0]))
{
x = atoi(argv[2]);
}
else
{
error = 1;
}


if (isdigit (argv[3][0]))
{
y = atoi(argv[3]);
}
else
{
error = 1;
}

}

if(error)
{
printf(" Usage: getPixel [ImagePath] [x] [y]\n");
printf(" ERROR, Please check the Image Path and [x, y] coordination !!\n");
return -1;
}

// OpenCV using BGR instead of RGB
CvScalar s = cvGet2D(img, y, x);
printf(" RGB : B=%d, G=%d, R=%d \n" , (int)s.val[0], (int)s.val[1], (int)s.val[2]);

hsv = cvCreateImage (cvGetSize (img), 8, 3);
cvCvtColor(img, hsv, CV_BGR2HSV);

s = cvGet2D(hsv, y, x);
printf(" HSV : H=%.2f, S=%.2f, V=%.2f \n" , s.val[0], s.val[1], s.val[2]);

cvNamedWindow("showImg");
// Mark the area
cvCircle(img, cvPoint(x, y), 4, cvScalar(255, 0, 0), 2);
cvShowImage("showImg", img);

cvWaitKey();

cvReleaseImage(&img);
cvReleaseImage(&hsv);

return 0;
}