如何在c ++中将ppm转换为bmp？

Question

我正在尝试用c ++实现光线跟踪器。我找到了一个生成ppm文件的代码。但是我正在尝试做一个bmp文件。如何在c ++代码中直接将ppm转换为bmp？我已经尝试过这个功能但是我的反思并不准确，所以我试图找到一个直接转换它的函数。

void savebmp (const char *filename, int w, int h, int dpi, Vec3f *data) {
    FILE *f;
    int k = w*h;
    int s = 4*k;
    int filesize = 54 + s;

    double factor = 39.375;
    int m = static_cast<int>(factor);

    int ppm = dpi*m;

    unsigned char bmpfileheader[14] = {'B','M', 0,0,0,0, 0,0,0,0, 54,0,0,0};
    unsigned char bmpinfoheader[40] = {40,0,0,0, 0,0,0,0, 0,0,0,0, 1,0,24,0};

    bmpfileheader[ 2] = (unsigned char)(filesize);
    bmpfileheader[ 3] = (unsigned char)(filesize>>8);
    bmpfileheader[ 4] = (unsigned char)(filesize>>16);
    bmpfileheader[ 5] = (unsigned char)(filesize>>24);

    bmpinfoheader[ 4] = (unsigned char)(w);
    bmpinfoheader[ 5] = (unsigned char)(w>>8);
    bmpinfoheader[ 6] = (unsigned char)(w>>16);
    bmpinfoheader[ 7] = (unsigned char)(w>>24);

    bmpinfoheader[ 8] = (unsigned char)(h);
    bmpinfoheader[ 9] = (unsigned char)(h>>8);
    bmpinfoheader[10] = (unsigned char)(h>>16);
    bmpinfoheader[11] = (unsigned char)(h>>24);

    bmpinfoheader[21] = (unsigned char)(s);
    bmpinfoheader[22] = (unsigned char)(s>>8);
    bmpinfoheader[23] = (unsigned char)(s>>16);
    bmpinfoheader[24] = (unsigned char)(s>>24);

    bmpinfoheader[25] = (unsigned char)(ppm);
    bmpinfoheader[26] = (unsigned char)(ppm>>8);
    bmpinfoheader[27] = (unsigned char)(ppm>>16);
    bmpinfoheader[28] = (unsigned char)(ppm>>24);

    bmpinfoheader[29] = (unsigned char)(ppm);
    bmpinfoheader[30] = (unsigned char)(ppm>>8);
    bmpinfoheader[31] = (unsigned char)(ppm>>16);
    bmpinfoheader[32] = (unsigned char)(ppm>>24);

    f = fopen(filename,"wb");

    fwrite(bmpfileheader,1,14,f);
    fwrite(bmpinfoheader,1,40,f);


    while (k>0) {
        for (int i=0; i<w; i++){
        double red = (data[k-w+i].x)*255;
        double green = (data[k-w+i].y)*255;
        double blue = (data[k-w+i].z)*255;

        unsigned char color[3] = {(int)floor(blue),(int)floor(green),(int)floor(red)};

        fwrite(color,1,3,f);
        }
        k=k-w;
    }

    fclose(f);
}