【darknet源碼解析-29】圖像RGB2HSV與HSV2RGB格式互轉

本系列爲darknet源碼解析，由於在image.c中涉及到圖像的RGB,YUV,HSV格式,在本文我們將image.c中涉及到的rgb_to_hsv()函數以及hsv_to_rgb()函數進行解析.

• RGB格式轉爲HSV格式

•  如果max=0

        

• 如果max!=0

         

       

       

       

對應源碼如下:

void rgb_to_hsv(image im)
{
    assert(im.c == 3);
    int i, j;
    float r, g, b;
    float h, s, v;
    for(j = 0; j < im.h; ++j){
        for(i = 0; i < im.w; ++i){
            r = get_pixel(im, i , j, 0);//獲取指定位置指定通道的像素值
            g = get_pixel(im, i , j, 1);
            b = get_pixel(im, i , j, 2);
            float max = three_way_max(r,g,b);//獲取rgb最大值
            float min = three_way_min(r,g,b);
            float delta = max - min;
            v = max;
            if(max == 0){
                s = 0;
                h = 0;
            }else{
                s = delta/max;
                if(r == max){
                    h = (g - b) / delta;
                } else if (g == max) {
                    h = 2 + (b - r) / delta;
                } else {
                    h = 4 + (r - g) / delta;
                }
                if (h < 0) h += 6;
                h = h/6.;
            }
            set_pixel(im, i, j, 0, h);//指定對應位置的對應通道的像素值
            set_pixel(im, i, j, 1, s);
            set_pixel(im, i, j, 2, v);
        }
    }
}

• HSV格式轉爲RGB格式

    

• 如果S==0:

      

• 如果S != 0:

       

       

       

      

對應源碼如下:

void hsv_to_rgb(image im)
{
    assert(im.c == 3);
    int i, j;
    float r, g, b;
    float h, s, v;
    float f, p, q, t;
    for(j = 0; j < im.h; ++j){
        for(i = 0; i < im.w; ++i){
            h = 6 * get_pixel(im, i , j, 0);
            s = get_pixel(im, i , j, 1);
            v = get_pixel(im, i , j, 2);
            if (s == 0) {
                r = g = b = v;
            } else {
                int index = floor(h);
                f = h - index;
                p = v*(1-s);
                q = v*(1-s*f);
                t = v*(1-s*(1-f));
                if(index == 0){
                    r = v; g = t; b = p;
                } else if(index == 1){
                    r = q; g = v; b = p;
                } else if(index == 2){
                    r = p; g = v; b = t;
                } else if(index == 3){
                    r = p; g = q; b = v;
                } else if(index == 4){
                    r = t; g = p; b = v;
                } else {
                    r = v; g = p; b = q;
                }
            }
            set_pixel(im, i, j, 0, r);
            set_pixel(im, i, j, 1, g);
            set_pixel(im, i, j, 2, b);
        }
    }
}

完.