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process specific pixels from an image

asked 2014-01-18 02:09:06 -0500

aparna gravatar image

d

How can i separate a specific region enclosed by the bounding box from the image and then process that specific region alone ??

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@JAyThaRevo never post links as solutions ... as they will possible disappear in the future this is not a good idea to make sure the solution is still available for other users when searching this forum. I will add a code snippet as answer.

StevenPuttemans gravatar imageStevenPuttemans ( 2014-01-23 07:20:03 -0500 )edit

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answered 2014-01-23 19:03:06 -0500

keghn gravatar image

updated 2014-01-24 02:06:06 -0500

Hi,

I am new to OpenCV. I was thinking my be you could hit the pixels you want with this program:


`#`include`<opencv2/highgui/highgui.hpp>`

`#`include`<stdio.h>`

`#`include`<iostream>`

using namespace cv;
using namespace std;

int main()
{
    Mat img = imread("red.jpg",CV_LOAD_IMAGE_COLOR);

    unsigned char *input = (unsigned char*)(img.data);
    unsigned int i,j,r,g,b;
    unsigned int r_Old,g_Old,b_Old;
    unsigned int r_average,g_average,b_average;
    uchar blue, green, red;
// dead center image read of a pixels of my image.jpg



   unsigned int y, x;

    y = 300;
    x = 300;
    Vec3b intensity = img.at<Vec3b>(y, x);


//The same method can be used to change pixel intensities: img.at<uchar>(y, x) = 128;
//have not written to image yet.


    blue = intensity.val[0];
    green = intensity.val[1];
    red = intensity.val[2];

    b_Old = blue;
    g_Old = green;
    r_Old = red;

    cout << "\n";
    cout << "b_Old " << b_Old << "\n";
    cout << "g__Old " << g_Old << "\n";
    cout << "r__Old " << r_Old << "\n";

        b_average = b_Old;
        g_average = g_Old;
        r_average = r_Old;

// i scaned the whole screen and averaged for an average color value:


    for( y = 0;y < img.rows;y++)
    {
    for( x = 0;x < img.cols;x++)
        {

    Vec3b intensity = img.at<Vec3b>(y, x);
    blue = intensity.val[0];
    green = intensity.val[1];
    red = intensity.val[2];

            b_average = b_average + blue;
            g_average = g_average + green;
            r_average = r_average + red;

            }

        }
    cout << "\n";

    b_average = b_average/(img.rows * img.cols);
    g_average = g_average/(img.rows * img.cols);
    r_average = r_average/(img.rows * img.cols);

    cout << "b_average " << b_average << "\n";
    cout << "g_average " << g_average << "\n";
    cout << "r_average " << r_average << "\n";
    cout << "img.rows " << img.rows << "\n";
    cout << "img.cols " << img.cols << "\n";

    return 0;
}

g++ -ggdb `pkg-config --cflags opencv` -o `basename p.cpp .cpp` p.cpp `pkg-config --libs opencv`

http://docs.opencv.org/doc/user_guide/ug_mat.html

g++ p.cpp -o p `pkg-config --cflags --libs opencv`

Worked on Mint Linux 14 in the terminal.

green.jpg(/upfiles/13905252524741347.jpg)(/upfiles/13905252303553609.jpg)

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Comments

Not to be rude, but your code does way more than what he actually asked for. Also, keep in mind in the future, that if a sortlike solution is given, it is better to add a comment with remarks, then readd a similar answer...

StevenPuttemans gravatar imageStevenPuttemans ( 2014-01-24 02:08:00 -0500 )edit
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answered 2014-01-24 18:26:19 -0500

keghn gravatar image
Vec3b intensity = img.at<Vec3b>(y, x);
blue = intensity.val[0];
green = intensity.val[1];
intensity.val[2] = 128;//ya, I can write to the image this way
red = intensity.val[2];
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answered 2014-01-23 07:25:08 -0500

This is possibly what you can do:

// This is pseudo-code, ofcourse you will need to change variable names with actual values or existing variables in your setup
// Region of interest - created manually or retrieved from somewhere
Rect bounding_box(x, y, width, heigth);
// Make a local copy of the region - do this to ensure you do not change the original image yet
Mat sub_region = original_image(bounding_box).clone();
// Perform something on this subregion --> for example apply Gaussian filter
GaussianBlur(sub_region, sub_region, Size(5,5), 0.0, 0.0, BORDER_DEFAULT );
// Copy the result back if you want it in your original image
sub_region.copyTo( original_image(bounding_box) );
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Asked: 2014-01-18 02:09:06 -0500

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Last updated: Jan 24 '14