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

#define MAG 0.8

void NearestNeighbor(unsigned char *out, unsigned char *in, int inHeight, int inWidth, int inChannel, double mag);

int main(){
   IplImage *in, *out;
   in = cvLoadImage("./image.bmp", 1);
   out = cvCreateImage(cvSize((int)(in->width*MAG), (int)(in->height*MAG)), 8, in->nChannels);

   NearestNeighbor((unsigned char*)out->imageData, (unsigned char*)in->imageData, in->height, in->width, in->nChannels, MAG);

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

   cvDestroyWindow("in");
   cvDestroyWindow("out");
   cvReleaseImage(&in);
   cvReleaseImage(&out);
   return 0;
}

/*
in : 横は4バイト
*/
void NearestNeighbor(unsigned char *out, unsigned char *in, int inHeight, int inWidth, int inChannel, double mag){
   int height;
   int width;
   int outStep;
   int inStep;
   int i, j;

   height = (int)((double)inHeight * mag);
   width = (int)((double)inWidth * mag);

   // OpenCVで使用する画像データの横幅は4バイト区切りのため調整
   inStep = inWidth * inChannel;
   if( (inStep % 4) != 0){
      inStep = inStep + (4 - inStep %4);
   }
   outStep = width * inChannel;
   if( (outStep % 4) != 0){
      outStep = outStep + (4 - outStep %4);
   }

   // ループ中にif文を書くと遅いためループ前にビット数の条件分岐
   switch(inChannel){
      case 1:
         // 8bit画像
         for(i = 0; i < height; ++i){
            for(j = 0; j < width; ++j){
               out[i * outStep + j] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag)];
            }
         }
         break;
      case 3:
         // 24bit画像
         for(i = 0; i < height; ++i){
            for(j = 0; j < width; ++j){
               out[i * outStep + j * 3] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 3];
               out[i * outStep + j * 3 + 1] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 3 + 1];
               out[i * outStep + j * 3 + 2] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 3 + 2];
            }
         }
         break;
      case 4:
         // 32bit画像
         for(i = 0; i < height; ++i){
            for(j = 0; j < width; ++j){
               out[i * outStep + j * 4] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 4];
               out[i * outStep + j * 4 + 1] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 4 + 1];
               out[i * outStep + j * 4 + 2] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 4 + 2];
               out[i * outStep + j * 4 + 3] = in[(int)((double)i/mag) * inStep + (int)((double)j/mag) * 4 + 3];
            }
         }
         break;
      default:
         break;
   }
}