Grayscale in Images - OPENCV

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Good afternoon Personal,

I have an image . bmp and want to turn it into grayscale (0-255), through Opencv with C++(I don’t want to save this image in grayscale). From there, I want to go through the image by doing the following:

For each pixel, if the grayscale is between 0-31, then this pixel belongs to class 1. If it is between 32-63 then this pixel belongs to class 2 ... and so on. We will thus have 8 classes.

Then I want to know how many pixels are part of class 1, 2, 3, ... , 8.

How can I do that? I searched the Opencv documentation but couldn’t find anything to help me with that.

Thank You Very Personal!

c++ image-processing opencv

  • Hello. Welcome to SOPT. This site is not a forum nor a ranked one. What have you done? What is your specific difficulty in this lot of things you want to do? If you haven’t done it yet, do the [tour]. Oh, and look here on the site yourself. There is a lot of content that can help you. Like this, for example: http://answall.com/questions/82354/edi%C3%A7%C3%A3o-de-imagens-using-opencv-sem-fun%C3%A7%C3%B5es-pronto

1 answer

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Mat img = imread("sua_imagem.bmp", CV_LOAD_IMAGE_GRAYSCALE);
vector<int> acumulador(8);

for (int i = 0; i < img.rows; i++)
    for (int j = 0; j < img.cols; j++) {
        int index = (int)img.at<uchar>(i, j) / 32;
        acumulador[index]++;
    }

this should solve your problem, the accumulator vector is size 8, where each position contains the number of pixels of the image belonging to that class.

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