Finding Face Algorithm

void findFace(DonneesImageRGB *img, int *xMin, int *yMin, int *xMax, int *yMax) {
    int i,j;
    float h,s,v;
    float r,g,b;

    for (i=img->hauteurImage/8; i<img->hauteurImage; i++)
        for (j=img->largeurImage/3; j<img->largeurImage*2/3; j++)
        {
            b = (float)(img->donneesRGB[(i*img->largeurImage + j)*3]) / 256 ;
            g = (float)(img->donneesRGB[(i*img->largeurImage + j)*3 + 1]) / 256 ;
            r = (float)(img->donneesRGB[(i*img->largeurImage + j)*3 + 2]) / 256 ;
            if (r > 0.4 && r < 0.6 && g > 0.22 && g < 0.33 && r > g && g > (1-r)/2)
            {
                convertRGBtoHSV(r,g,b,&h,&s,&v);
                if (h > 0 && h < 0.2 && s > 0.3 && s < 0.7 && v > 0.22 && v < 0.8)
                {
                    if (j < *xMin)
                        *xMin = j;
                    if (i < *yMin)
                        *yMin = i;
                    if (j > *xMax)
                        *xMax = j;
                    if (i > *yMax)
                        *yMax = i;
                }
            }
        }
}