#include <math.h>
#include <cxcore.h>
#include <cv.h>
#include <highgui.h>
#pragma comment(lib,"cv.lib")
#pragma comment(lib,"cxcore.lib")
#pragma comment(lib,"highgui.lib")

void sobel(unsigned char *out, unsigned char *in, int inHeight, int inWidth, int inChannel);

int main(){
    IplImage *in, *out;

    in = cvLoadImage("./image.bmp", 0);
    out = cvCreateImage(cvSize(in->width, in->height), in->depth, in->nChannels);
    
    sobel((unsigned char*)out->imageData, (unsigned char*)in->imageData, in->height, in->width, in->nChannels);

    cvNamedWindow("in", 1);
    cvShowImage("in", in);
    cvNamedWindow("out", 1);
    cvShowImage("out", out);
    cvWaitKey(-1);
    
    cvDestroyWindow("in");
    cvDestroyWindow("out");

    cvReleaseImage( &in );
    cvReleaseImage( &out );

    return 0;
}

/*
端は処理していない
*/
void sobel(unsigned char *out, unsigned char *in, int inHeight, int inWidth, int inChannel){
    int i, j, k, l;
    int weightH[9] = {-1, 0, 1,
                     -2, 0, 2,
                     -1, 0, 1};
    int weightV[9] = {-1, -2, -1,
                      0,  0,  0,
                      1,  2,  1};
    int *imgTmp;
    int weightSize = 3;

    int start = -1;
    int end = start + weightSize;
    double dataTmpH;
    double dataTmpV;
    double dataTmpSum;
    int widthStep;

    widthStep = inWidth * inChannel;
    if(widthStep % 4 != 0){
        widthStep = widthStep + 4 - widthStep % 4;
    }

    for(i = 1; i < (inHeight - 1); ++i){
        for(j = 1; j < (inWidth - 1); ++j){
            dataTmpH = 0;
            dataTmpV = 0;
            for(k = start; k < end; ++k){
                for(l = start; l < end; ++l){
                    // 水平方向
                    dataTmpH += weightH[(k - start) * weightSize + (l - start)] * (unsigned char)in[(i + k) * widthStep + (j + l)];

                    // 垂直方向
                    dataTmpV += weightV[(k - start) * weightSize + (l - start)] * (unsigned char)in[(i + k) * widthStep + (j + l)];

                }
            }
            dataTmpSum = sqrt(dataTmpH * dataTmpH + dataTmpV * dataTmpV);
            
            // 255を超えた値は255、0未満の値は絶対値
            if(dataTmpSum > 255){
                dataTmpSum = 255;
            } else if(dataTmpSum < 0){
                dataTmpSum = -dataTmpSum;
            }
            out[i * widthStep + j] = dataTmpSum;
        }
    }

}