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?

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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

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1

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