c=imread('G:LEARNINGImage_Processing_MATLABimdataLenna.png');
c(:,:,2)=0;
c(:,:,3)=0;
imshow(c)

for (int k = 0; k<img.step[1]; k++)
{
    for (int i = 0; i< img.rows; i++) //run through out the rows
    {
        for (int j = 0; j< img.cols; j++)//run through out the cols
        {
            if ((k == 0) || (k == 1))
            {
                *(img.data + k + img.step[0] * i + j*img.step[1]) = 0;
            }

        }
    }
}