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- -- http://axonflux.com/handy-rgb-to-hsl-and-rgb-to-hsv-color-model-c
- --[[
- * Converts an RGB color value to HSL. Conversion formula
- * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
- * Assumes r, g, and b are contained in the set [0, 255] and
- * returns h, s, and l in the set [0, 1].
- *
- * @param Number r The red color value
- * @param Number g The green color value
- * @param Number b The blue color value
- * @return Array The HSL representation
- ]]
- function rgbToHsl(r, g, b, a)
- r, g, b = r / 255, g / 255, b / 255
- local max, min = math.max(r, g, b), math.min(r, g, b)
- local h, s, l
- l = (max + min) / 2
- if max == min then
- h, s = 0, 0 -- achromatic
- else
- local d = max - min
- local s
- if l > 0.5 then s = d / (2 - max - min) else s = d / (max + min) end
- if max == r then
- h = (g - b) / d
- if g < b then h = h + 6 end
- elseif max == g then h = (b - r) / d + 2
- elseif max == b then h = (r - g) / d + 4
- end
- h = h / 6
- end
- return h, s, l, a or 255
- end
- --[[
- * Converts an HSL color value to RGB. Conversion formula
- * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
- * Assumes h, s, and l are contained in the set [0, 1] and
- * returns r, g, and b in the set [0, 255].
- *
- * @param Number h The hue
- * @param Number s The saturation
- * @param Number l The lightness
- * @return Array The RGB representation
- ]]
- function hslToRgb(h, s, l, a)
- local r, g, b
- if s == 0 then
- r, g, b = l, l, l -- achromatic
- else
- function hue2rgb(p, q, t)
- if t < 0 then t = t + 1 end
- if t > 1 then t = t - 1 end
- if t < 1/6 then return p + (q - p) * 6 * t end
- if t < 1/2 then return q end
- if t < 2/3 then return p + (q - p) * (2/3 - t) * 6 end
- return p
- end
- local q
- if l < 0.5 then q = l * (1 + s) else q = l + s - l * s end
- local p = 2 * l - q
- r = hue2rgb(p, q, h + 1/3)
- g = hue2rgb(p, q, h)
- b = hue2rgb(p, q, h - 1/3)
- end
- return r * 255, g * 255, b * 255, a * 255
- end
- --[[
- * Converts an RGB color value to HSV. Conversion formula
- * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
- * Assumes r, g, and b are contained in the set [0, 255] and
- * returns h, s, and v in the set [0, 1].
- *
- * @param Number r The red color value
- * @param Number g The green color value
- * @param Number b The blue color value
- * @return Array The HSV representation
- ]]
- function rgbToHsv(r, g, b, a)
- r, g, b, a = r / 255, g / 255, b / 255, a / 255
- local max, min = math.max(r, g, b), math.min(r, g, b)
- local h, s, v
- v = max
- local d = max - min
- if max == 0 then s = 0 else s = d / max end
- if max == min then
- h = 0 -- achromatic
- else
- if max == r then
- h = (g - b) / d
- if g < b then h = h + 6 end
- elseif max == g then h = (b - r) / d + 2
- elseif max == b then h = (r - g) / d + 4
- end
- h = h / 6
- end
- return h, s, v, a
- end
- --[[
- * Converts an HSV color value to RGB. Conversion formula
- * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
- * Assumes h, s, and v are contained in the set [0, 1] and
- * returns r, g, and b in the set [0, 255].
- *
- * @param Number h The hue
- * @param Number s The saturation
- * @param Number v The value
- * @return Array The RGB representation
- ]]
- function hsvToRgb(h, s, v, a)
- local r, g, b
- local i = Math.floor(h * 6);
- local f = h * 6 - i;
- local p = v * (1 - s);
- local q = v * (1 - f * s);
- local t = v * (1 - (1 - f) * s);
- i = i % 6
- if i == 0 then r, g, b = v, t, p
- elseif i == 1 then r, g, b = q, v, p
- elseif i == 2 then r, g, b = p, v, t
- elseif i == 3 then r, g, b = p, q, v
- elseif i == 4 then r, g, b = t, p, v
- elseif i == 5 then r, g, b = v, p, q
- end
- return r * 255, g * 255, b * 255, a * 255
- end
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