Gradient.cpp

#include "Gradient.h"
#include "LinearMapper.h"
#include "macroses.h"

namespace DirectGraphicalModels { namespace fex
{
Mat CGradient::get(const Mat &img, float mid)
{
    DGM_ASSERT(mid <= GRADIENT_MAX_VALUE);
    DGM_ASSERT(mid > 0);
     
    // Converting to one channel image
    Mat I;
    if (img.channels() != 1) cvtColor(img, I, cv::ColorConversionCodes::COLOR_RGB2GRAY);
    else img.copyTo(I);
    
    // Derivatives
    Mat Ix = getDerivativeX(I);
    Mat Iy = getDerivativeY(I);

    // Magnitude
    Mat res(img.size(), CV_8UC1);       // gradient     
    for(int y = 0; y < img.rows; y++) { 
        float *pIx  = Ix.ptr<float>(y);
        float *pIy  = Iy.ptr<float>(y);
        for(int x = 0; x < img.cols; x++) {
            float val = sqrtf(pIx[x]*pIx[x] + pIy[x]*pIy[x]);
            res.at<byte>(y,x) = two_linear_mapper<byte>(val, 0, GRADIENT_MAX_VALUE, mid, 255);
        }
    } // y  

    return res;
}

Mat CGradient::getDerivativeX(const Mat &img)
{
    DGM_ASSERT(img.channels() == 1);
    
    Mat res(img.size(), CV_32FC1); res.setTo(0);
    for(int y = 0; y < res.rows; y++) {
        const byte  *pImg   = img.ptr<byte>(y);
        float       *pRes   = res.ptr<float>(y);
        for(int x = 1; x < res.cols - 1; x++)
            pRes[x] = 0.5f * (static_cast<float>(pImg[x + 1]) - static_cast<float>(pImg[x - 1]));
    } // y
    return res;
}

Mat CGradient::getDerivativeY(const Mat &img)
{
    DGM_ASSERT(img.channels() == 1);
    
    Mat res(img.size(), CV_32FC1); res.setTo(0);
    for(int y = 1; y < res.rows - 1; y++) {
        const byte  *pImgF  = img.ptr<byte>(y + 1);
        const byte  *pImgB  = img.ptr<byte>(y - 1);
        float       *pRes   = res.ptr<float>(y);
        for(int x = 0; x < res.cols; x++)
            pRes[x] = 0.5f * (static_cast<float>(pImgF[x]) - static_cast<float>(pImgB[x]));
    } // y
    return res;
}

} }