Merging channels in OpenCV

I need to create a 'red' image from a grayscale image. I am using this code:

void build_red(const cv::Mat& in, cv::Mat& out) {
    out = Mat::zeros(in.rows, in.cols, CV_8UC1);

    Mat zeros = Mat::zeros(in.rows, in.cols, CV_8UC1);
    Mat tmp;
    in.convertTo(tmp, CV_8UC1);

    vector<Mat> ch;
    ch.push_back(zeros);
    ch.push_back(zeros);
    ch.push_back(tmp);

    cout << "Using " << ch.size() << " channels" << endl;
    merge(ch, out);
} // build_red

With some explanations:

void build_red(const cv::Mat& in, cv::Mat& out) {

in is the input matrix, out the output.

out = Mat::zeros(in.rows, in.cols, CV_8UC1);

allocate some space for out (may be useless, but part of my attempts)

    Mat zeros = Mat::zeros(in.rows, in.cols, CV_8UC1);
    Mat tmp;
    in.convertTo(tmp, CV_8UC1);

Create an empty matrix with the same size and convert the input image to single-channel uchar.

    vector<Mat> ch;
    ch.push_back(zeros);
    ch.push_back(zeros);
    ch.push_back(tmp);

    cout << "Using " << ch.size() << " channels" << endl;
    merge(ch, out);

Create a vector with three channels, then merge them into 'out'.

However, when I run the code I get the following message:

     Using 3 channels

and the following exception:

OpenCV Error: Bad number of channels (Source image must have 1, 3 or 4 channels) 
in cvConvertImage, file /[...]/libs/OpenCV-2.4.0/modules/highgui/src/utils.cpp, 
line 611
terminate called after throwing an instance of 'cv::Exception'
what():  /[...]/libs/OpenCV-2.4.0/modules/highgui/src/utils.cpp:611: 
error: (-15) Source image must have 1, 3 or 4 channels in function cvConvertImage

Could you please help me? From my inexperienced point of view, the type of the images is the same and the number of channels is correct.

---

Why are you converting the image if you have a grayscale image present?

Just create two empty matrix of the same size for Blue and Green.

And you have defined your output matrix as 1 channel matrix. Your output matrix must contain at least 3 channels. (Blue, Green and Red). Where Blue and Green will be completely empty and you put your grayscale image as Red channel of the output image.

#include <opencv2/highgui/highgui.hpp> 
#include <stdio.h>
using namespace std;
using namespace cv;

int main()
{
    Mat img, g, fin_img;
    img = imread("Lenna.png",CV_LOAD_IMAGE_GRAYSCALE);
    vector<Mat> channels;

    g = Mat::zeros(Size(img.rows, img.cols), CV_8UC1);

    channels.push_back(g);
    channels.push_back(g);
    channels.push_back(img);

    merge(channels, fin_img);
    imshow("img", fin_img);
    waitKey(0);
    return 0;
}

链接地址: http://www.djcxy.com/p/67006.html

上一篇: 使用OpenCV和SVM与图像

下一篇: 合并OpenCV中的通道