c++ - OpenCV: A straighforward method of colorizing a grayscale image -

what straight forward method of "colorizing" grayscale image. colorizing, mean porting grayscale intensity values 1 of 3 r, g, b channels in new image.

for example 8uc1 grayscale pixel intensity of i = 50 should become 8uc3 color pixel of intensity bgr = (50, 0, 0) when picture colorized "blue".

in matlab example, i'm asking can created 2 lines of code:

color_im = zeros([size(gray_im) 3], class(gray_im)); color_im(:, :, 3) = gray_im;  

but amazingly cannot find similar in opencv.

well, same thing requires bit more work in c++ , opencv:

// load single-channel grayscale image cv::mat gray = cv::imread("filename.ext", cv_load_image_grayscale);  // create empty matrix of same size (for 2 empty channels) cv::mat empty = cv::mat::zeros(gray.size(), cv_8uc1);  // create vector containing channels of new colored image std::vector<cv::mat> channels;  channels.push_back(gray);   // 1st channel channels.push_back(empty);  // 2nd channel channels.push_back(empty);  // 3rd channel  // construct new 3-channel image of same size , depth cv::mat color; cv::merge(channels, color); 

or function (compacted):

cv::mat colorize(cv::mat gray, unsigned int channel = 0) {     cv_assert(gray.channels() == 1 && channel <= 2);      cv::mat empty = cv::mat::zeros(gray.size(), gray.depth());     std::vector<cv::mat> channels(3, empty);     channels.at(channel) = gray;      cv::mat color;     cv::merge(channels, color);     return color; }