Is there a simple method to highlight the mask?

highlight

asked 2017-09-07 14:22:32 -0600

yode
185 ●2 ●9

updated 2017-09-07 14:25:42 -0600

If I have mask like

And I have a image( the size is same to the mask) like

Mathematica graphics

I want to hightlight the mask in the image. If I'm in other Language,I just

As you can see, the result image have a transparent red show the mask. I hope implement this in OpenCV. So I write this code

#include <opencv.hpp>

using namespace cv;
using namespace std;

int main() {
    Mat srcImg = imread("image.jpg");
    Mat mask = imread("mask.jpg", IMREAD_GRAYSCALE)>200;

    for(int i=0;i<srcImg.rows;i++)
        for(int j=0;j<srcImg.cols;j++)
            if(mask.at<uchar>(i, j)==255)
                circle(srcImg, Point(j,i), 3, Scalar(0, 0, 128,128));
    imshow("image",srcImg);

    waitKey();
    return 0;
}

But as you see, I use a alpha value in Scalar, but it is not a transparent red.

Maybe this is due to the srcImg just have 3 channels. I have two question about this

How to hightlight the mask with a transparent red(even the image just have 3 channels)?
I have to draw circle pixel by pixel to do this thing?

edit retag flag offensive close merge delete

Comments

there is no alpha channel in image processing but you can use this tutorial

LBerger ( 2017-09-07 14:28:44 -0600 )edit

@LBerger Thanks,but it is not a transparent red..Just a transprent whilte..

yode ( 2017-09-07 14:36:35 -0600 )edit

replace circle(srcImg, Point(j,i), 3, Scalar(0, 0, 128,128)); with srcImg.at<Vec3b>(i, j) = srcImg.at<Vec3b>(i, j) - Vec3b(100, 100, 0);

sturkmen ( 2017-09-07 15:26:52 -0600 )edit

also take a look at this i prefer doing this kind of operations without pixel by pixel approach

sturkmen ( 2017-09-07 15:32:21 -0600 )edit

add a comment

2 answers

Sort by » oldest newest most voted

answered 2017-09-07 16:18:42 -0600

sturkmen

6772 ●3 ●48 ●79 https://github.com/stu...

you can replace

circle(srcImg, Point(j,i), 3, Scalar(0, 0, 128,128));

with

srcImg.at<Vec3b>(i, j) = srcImg.at<Vec3b>(i, j) - Vec3b(100, 100, 0);

but i prefer the way below

#include<opencv2/core.hpp>
#include<opencv2/imgproc.hpp>
#include<opencv2/highgui.hpp>

using namespace cv;

int main(int argc, char** argv)
{
    Mat srcImg = imread("image.png");
    Mat mask = imread("mask.png", IMREAD_GRAYSCALE) > 200;

    Mat red;
    cvtColor(mask, red, COLOR_GRAY2BGR);
    red = (red - Scalar(0, 0, 255)) / 2;
    srcImg = srcImg - red;

    imshow("image", srcImg);

    waitKey();
    return 0;
}

image description