Get all pixel coordinates that have the same color

Question

I want to get all the coordinates of pixels that have the same color as one pixel

List<cv::Point> GetAllPixels(cv::Point x) { //imp } 

How to do it in EmguCV or OpenCV?

Answer 1

Here is a possible solution using OpenCV C ++:

 #include <opencv2/core/core.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <vector> using namespace std; using namespace cv; std::vector<cv::Point> getPixelsWithColor(const cv::Mat& src, cv::Scalar targetColor) { assert(src.type() == CV_8UC3); std::vector<cv::Point> identicalPoints; for(int row = 0; row < src.rows; ++row) { for(int col = 0; col < src.cols; ++col) { cv::Vec3b currPixel = src.at<cv::Vec3b>(row, col); if(currPixel[0] == targetColor.val[0] && currPixel[1] == targetColor.val[1] && currPixel[2] == targetColor.val[2]) { identicalPoints.push_back(cv::Point(col, row)); } } } return identicalPoints; } int main(int argc, char** argv) { Mat squares = imread("colored_squares.png"); const Scalar RED = Scalar(0, 0, 255); // OpenCV is BGR order... vector<Point> redPixelLocations; redPixelLocations = getPixelsWithColor(squares, RED); Mat redMask = Mat::zeros(squares.size(), CV_8UC1); vector<Point>::iterator i; for(i = redPixelLocations.begin(); i != redPixelLocations.end(); ++i) { redMask.at<uchar>(*i) = 255; } imshow("Squares", squares); imshow("Red mask", redMask); waitKey(); return 0; } 

I used this input image:

And reached this output image:

Enjoy! :)

Answer 2

The answer should begin. Also consider using the Cmp function Cmp

For IplImage might be something like this:

 IplImage *img, *col_img, *mask_img; // initialise images appropriately... svSet(col_img, [colour of your choise]); cvCmp(img, col_img, mask_img, CV_CMP_EQ); 

Use mask_img to extract the coordinates. You can find equivalent operations for cv::Mat .