node_color.h

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/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/* Color Management */

float color_srgb_to_scene_linear(float c)
{
    if(c < 0.04045)
        return (c < 0.0)? 0.0: c * (1.0/12.92);
    else
        return pow((c + 0.055)*(1.0/1.055), 2.4);
}

float color_scene_linear_to_srgb(float c)
{
    if(c < 0.0031308)
        return (c < 0.0)? 0.0: c * 12.92;
    else
        return 1.055 * pow(c, 1.0/2.4) - 0.055;
}

color color_srgb_to_scene_linear(color c)
{
    return color(
        color_srgb_to_scene_linear(c[0]),
        color_srgb_to_scene_linear(c[1]),
        color_srgb_to_scene_linear(c[2]));
}

color color_scene_linear_to_srgb(color c)
{
    return color(
        color_scene_linear_to_srgb(c[0]),
        color_scene_linear_to_srgb(c[1]),
        color_scene_linear_to_srgb(c[2]));
}

/* Color Operations */

color rgb_to_hsv(color rgb)
{
    float cmax, cmin, h, s, v, cdelta;
    color c;

    cmax = max(rgb[0], max(rgb[1], rgb[2]));
    cmin = min(rgb[0], min(rgb[1], rgb[2]));
    cdelta = cmax - cmin;

    v = cmax;

    if(cmax != 0.0) {
        s = cdelta/cmax;
    }
    else {
        s = 0.0;
        h = 0.0;
    }

    if(s == 0.0) {
        h = 0.0;
    }
    else {
        c = (color(cmax, cmax, cmax) - rgb)/cdelta;

        if(rgb[0] == cmax) h = c[2] - c[1];
        else if(rgb[1] == cmax) h = 2.0 + c[0] -  c[2];
        else h = 4.0 + c[1] - c[0];

        h /= 6.0;

        if(h < 0.0)
            h += 1.0;
    }

    return color(h, s, v);
}

color hsv_to_rgb(color hsv)
{
    float i, f, p, q, t, h, s, v;
    color rgb;

    h = hsv[0];
    s = hsv[1];
    v = hsv[2];

    if(s==0.0) {
        rgb = color(v, v, v);
    }
    else {
        if(h==1.0)
            h = 0.0;
        
        h *= 6.0;
        i = floor(h);
        f = h - i;
        rgb = color(f, f, f);
        p = v*(1.0-s);
        q = v*(1.0-(s*f));
        t = v*(1.0-(s*(1.0-f)));
        
        if(i == 0.0) rgb = color(v, t, p);
        else if(i == 1.0) rgb = color(q, v, p);
        else if(i == 2.0) rgb = color(p, v, t);
        else if(i == 3.0) rgb = color(p, q, v);
        else if(i == 4.0) rgb = color(t, p, v);
        else rgb = color(v, p, q);
    }

    return rgb;
}