#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 1.5

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

int main(){
    IplImage *in, *out;
    in = cvLoadImage("./image640.bmp", 1);
    out = cvCreateImage(cvSize((int)(in->width*MAG), (int)(in->height*MAG)), 8, in->nChannels);

    Bilinear((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 Bilinear(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;
    double inX, inY;

    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){
                inY = (double)i / mag;
                // 入力画像の高さを超えないようにする
                if((int)inY >= inHeight){
                    --inY;
                }
                for(j = 0; j < width; ++j){
                    // 入力画像の幅を超えないようにする
                    inX = (double)j / mag;
                    if((int)inX >= inWidth){
                        --inX;
                    }
                    out[i * outStep + j] = (unsigned char)(((int)inX + 1 - inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + (int)inX]
                                            + (inX - (int)inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + (int)inX + 1]
                                            + ((int)inX + 1 - inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + (int)inX]
                                            + (inX - (int)inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + (int)inX + 1]);

                }
            }
            break;
        case 3:
            // 24bit画像
            for(i = 0; i < height; ++i){
                inY = (double)i / mag;
                // 入力画像の高さを超えないようにする
                if((int)inY >= inHeight){
                    --inY;
                }
                for(j = 0; j < width; ++j){
                    // 入力画像の幅を超えないようにする
                    inX = (double)j / mag;
                    if((int)inX >= inWidth){
                        --inX;
                    }
                    out[i * outStep + j * 3] = (unsigned char)(((int)inX + 1 - inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + (int)inX * 3]
                                            + (inX - (int)inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + ((int)inX + 1) * 3]
                                            + ((int)inX + 1 - inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + (int)inX * 3]
                                            + (inX - (int)inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + ((int)inX + 1) * 3]);
                    out[i * outStep + j * 3 + 1] = (unsigned char)(((int)inX + 1 - inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + (int)inX * 3 + 1]
                                            + (inX - (int)inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + ((int)inX + 1) * 3 + 1]
                                            + ((int)inX + 1 - inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + (int)inX * 3 + 1]
                                            + (inX - (int)inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + ((int)inX + 1) * 3 + 1]);
                    out[i * outStep + j * 3 + 2] = (unsigned char)(((int)inX + 1 - inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + (int)inX * 3 + 2]
                                            + (inX - (int)inX) * ((int)inY + 1 - inY) * (double)in[(int)inY * inStep + ((int)inX + 1) * 3 + 2]
                                            + ((int)inX + 1 - inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + (int)inX * 3 + 2]
                                            + (inX - (int)inX) * (inY - (int)inY) * (double)in[((int)inY + 1) * inStep + ((int)inX + 1) * 3 + 2]);

                }
            }
            break;
        case 4:
            // 32bit画像
            break;
        default:
            break;
    }
}