사용한 라이브러리

Q.39. JPEG 압축 (Step.3) YCbCr 표색계

struct YCbCr
{
    double Y, Cb, Cr;
};
struct RGB
{
    RGB(int r, int g, int b)
    {
        this->r = r;
        this->g = g;
        this->b = b;
    }
    int r, g, b;
};

YCbCr RGB2YCbCr(const RGB& rgb)
{
    YCbCr ycbcr;
    int R = rgb.r;
    int G = rgb.g;
    int B = rgb.b;

    ycbcr.Y = 0.299 * R + 0.5870 * G + 0.114 * B;
    ycbcr.Cb = -0.1687 * R - 0.3313 * G + 0.5 * B + 128;
    ycbcr.Cr = 0.5 * R - 0.4187 * G - 0.0813 * B + 128;

    return ycbcr;
}
RGB YCbCr2RGB(const YCbCr& ycbcr)
{
    double R, G, B;
    double Y = ycbcr.Y;
    double Cb = ycbcr.Cb;
    double Cr = ycbcr.Cr;
    R = Y + (Cr - 128) * 1.402;
    G = Y - (Cb - 128) * 0.3441 - (Cr - 128) * 0.7139;
    B = Y + (Cb - 128) * 1.7718;
    return RGB(R,G,B);
}

int main()
{
    PPM ppm("imori.pnm");
    int width = ppm.Get_width();
    int height = ppm.Get_height();
    PPM ppm2(width, height);

    for (int j = 0; j < height; j++)
        for (int i = 0; i < width; i++)
        {
            int r = ppm(i, j, 'r');
            int g = ppm(i, j, 'g');
            int b = ppm(i, j, 'b');

            YCbCr ycbcr = RGB2YCbCr(RGB(r, g, b));
            ycbcr.Y *= 0.7;

            RGB rgb = YCbCr2RGB(ycbcr);
            ppm2(i, j, 'r') = rgb.r;
            ppm2(i, j, 'g') = rgb.g;
            ppm2(i, j, 'b') = rgb.b;
        }

    ppm2.Flush("out.ppm");
    return 0;
}