CODEWITHSUNDEEP
c++visual-studio-2010imageopencvimage-processing
PeakGen
PeakGen

Reputation: 23025

Sharpening an Image - Accessing neighbor pixels

I am working on the following code:

#include <iostream>
#include <opencv2\core\core.hpp>
#include <opencv2\highgui\highgui.hpp>

using namespace std;
using namespace cv;

void Sharpen(Mat &,Mat);

int main()
{
    Mat image,result;

    try
    {
        image = imread("C:/Users/Public/Pictures/Sample Pictures/Desert.jpg");

        if(!image.data)
        {
            throw 1;
        }
    }
    catch(int i)
    {
        cout << "Image is unable to reae" << endl;
    }

    Sharpen(image,result);
    waitKey(0);
}

void Sharpen(Mat &image,Mat result)
{
    //result = image.clone();
    result.create(image.size(), image.type());

    //For all rows except first and last
    for(int i=1;i<image.rows-1;i++)
    {
        const uchar *previous = image.ptr<const uchar>(i-1);
        const uchar *next = image.ptr<const uchar>(i+1);
        const uchar *current = image.ptr<const uchar>(i);

        uchar *output = result.ptr<uchar>(i);

        //For all columns except first and last
        for(int a=1;a<image.cols-1;a++)
        {
            *output++ = cv::saturate_cast<uchar>(5*current[a]-current[a-1]-current[a+1]-previous[a]-next[a]);
        }

    }

    result.row(0).setTo(cv::Scalar(0));
    result.row(result.rows-1).setTo(cv::Scalar(0));
    result.col(0).setTo(cv::Scalar(0));
    result.col(result.cols-1).setTo(cv::Scalar(0));

    namedWindow("Original");
    imshow("Original",image);

    namedWindow("Duplicate");
    imshow("Duplicate",result);
}

In here, what I an trying to do is, trying to sharpen an image. Following is the formula for image sharpening.

resultPixel = 5*currentPixel-previousPixel-nextPixel-upperPixel-belowPixel

Anyway, following is the output I get

enter image description here

As you can see, I am not getting the expected result. What am doing wrong?

Upvotes: 2

Views: 4092

Answers (1)

Peter R
Peter R

Reputation: 2985

Your first issue is that there are 3 bytes per pixel so you are only iterating over a third of your image. Your other issue is that you cannot do *output++ as you want to skip the first pixel. Putting those two things together results in the following code which gives the result you are looking for.

#include <iostream>
#include <opencv2\core\core.hpp>
#include <opencv2\highgui\highgui.hpp>

using namespace std;
using namespace cv;

void Sharpen(Mat &image,Mat& result)
{
    result.create(image.size(), image.type());

    //For all rows except first and last
    for(int i=1;i<image.rows-1;i++)
    {
        const uchar *previous = image.ptr<const uchar>(i-1);
        const uchar *next = image.ptr<const uchar>(i+1);
        const uchar *current = image.ptr<const uchar>(i);

        uchar *output = result.ptr<uchar>(i);

        //For all columns except first and last
        for(int a=3;a<(image.cols-1)*3;a++)
        {
            output[a] = cv::saturate_cast<uchar>(5*current[a]-current[a-1]-current[a+1]-previous[a]-next[a]);
        }

    }

    result.row(0).setTo(cv::Scalar(0));
    result.row(result.rows-1).setTo(cv::Scalar(0));
    result.col(0).setTo(cv::Scalar(0));
    result.col(result.cols-1).setTo(cv::Scalar(0));

    namedWindow("Original");
    imshow("Original",image);

    namedWindow("Duplicate");
    imshow("Duplicate",result);

}

int main()
{
    Mat image,result;

    try
    {
        image = imread("C:/Users/Public/Pictures/Sample Pictures/Desert.jpg");

        if(!image.data)
        {
            throw 1;
        }
    }
    catch(int i)
    {
        cout << "Image is unable to reae" << endl;
    }

    Sharpen(image,result);
    waitKey(0);
}

Upvotes: 3

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