node_color.h

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/*
 * Copyright 2011-2013 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
/* TODO(lukas): Fix colors in OSL. */
 
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 color_unpremultiply(color c, float alpha)
{
  if (alpha != 1.0 && alpha != 0.0)
    return c / alpha;
 
  return c;
}
 
/* Color Operations */
 
color xyY_to_xyz(float x, float y, float Y)
{
  float X, Z;
 
  if (y != 0.0)
    X = (x / y) * Y;
  else
    X = 0.0;
 
  if (y != 0.0 && Y != 0.0)
    Z = ((1.0 - x - y) / y) * Y;
  else
    Z = 0.0;
 
  return color(X, Y, Z);
}
 
color xyz_to_rgb(float x, float y, float z)
{
  return color(3.240479 * x + -1.537150 * y + -0.498535 * z,
               -0.969256 * x + 1.875991 * y + 0.041556 * z,
               0.055648 * x + -0.204043 * y + 1.057311 * z);
}
 
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;
}