"colorsys" --- 颜色系统间的转换
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**源代码：** Lib/colorsys.py

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The "colorsys" module defines bidirectional conversions of color
values between colors expressed in the RGB (Red Green Blue) color
space used in computer monitors and three other coordinate systems:
YIQ, HLS (Hue Lightness Saturation) and HSV (Hue Saturation Value).
Coordinates in all of these color spaces are floating-point values.
In the YIQ space, the Y coordinate is between 0 and 1, but the I and Q
coordinates can be positive or negative.  In all other spaces, the
coordinates are all between 0 and 1.

参见:

  有关色彩空间的更多信息可访问 https://poynton.ca/ColorFAQ.html 和
  https://www.cambridgeincolour.com/tutorials/color-spaces.htm。

The "colorsys" module defines the following functions:

colorsys.rgb_to_yiq(r, g, b)

   把颜色从 RGB 坐标转为 YIQ 坐标。

colorsys.yiq_to_rgb(y, i, q)

   把颜色从 YIQ 坐标转为 RGB 坐标。

colorsys.rgb_to_hls(r, g, b)

   把颜色从 RGB 坐标转为 HLS 坐标。

colorsys.hls_to_rgb(h, l, s)

   把颜色从 HLS 坐标转为 RGB 坐标。

colorsys.rgb_to_hsv(r, g, b)

   把颜色从 RGB 坐标转为 HSV 坐标。

colorsys.hsv_to_rgb(h, s, v)

   把颜色从 HSV 坐标转为 RGB 坐标。

示例:

   >>> import colorsys
   >>> colorsys.rgb_to_hsv(0.2, 0.4, 0.4)
   (0.5, 0.5, 0.4)
   >>> colorsys.hsv_to_rgb(0.5, 0.5, 0.4)
   (0.2, 0.4, 0.4)
