c++ - Converting contours from vector of cv::Point in cv::Mat -

suppose objective extract contours initial image. performed operations using opencv:

cv::mat gray, edges; cv::cvtcolor(image, gray, cv_bgra2gray); cv::canny(gray, edges, 100, 300, 3);  std::vector<std::vector<cv::point>> contours; std::vector<cv::vec4i> hierarchy; cv::findcontours(edges, contours, hierarchy, cv::retr_tree, cv::chain_approx_simple, cv::point(0, 0)); 

now contour contained in array of points. want rebuild cv::mat structure having same dimensions initial image, emphasize contour superimposing image.

in particular, not interested in drawing contour. perform following operations:

• extract contour
• dilate contour
• superimpose contour on image (as in edge sharpening)

thus, contour has matrix of same size of input image.

how can that?

thanks in advance.

you can re-built matrix

mat image_contours_grayscale = mat::zeros(gray.size(),gray.type()); scalar color(255); drawcontours( image_contours_grayscale, contours,-1,color,1); 

i'm not sure if drawcontours works grayscale image, if doesn't, can try

mat image_contours_color = mat::zeros(image.size(),image.type()); scalar color(255,255,255); drawcontours( image_contours_color, contours,-1,color,1); mat image_contours_grayscale; cv::cvtcolor(image_contours_color, image_contours_grayscale, cv_bgra2gray); 

image_contours_grayscale should grayscale image, black contours in white.

let me know if works, didn't have occasion test solution !