How to measure differences between colors that near linear to human perception.

• CIE Delta Lab / CIE E76 / dE76: Simple, error prone
• CIE Delta E2000 / CIEDE2000 / dE00: Slightly complicated, more accurate

• Larger deltas means more noticeable
• dE76: ~ 2.3 corresponds to a JND (just noticeable difference).
• dE00:
  • <= 1.0: Not perceptible by human eyes.
  • 1 - 2: Perceptible through close observation.
  • 2 - 10: Perceptible at a glance.
  • 11 - 49: Colors are more similar than opposite
  • 100: Colors are exact opposite

• Python 3
• cv2 >=3

• This module works mainly with OpenCV, so the input color channel for delta functions are in BGR color space.
• This module use OpenCV merely as a color space translator from BGR => XYZ => Lab.
• Read doctring of the wrapper _cvt_bgr2lab function before reuse it outside this module.

• http://zschuessler.github.io/DeltaE/learn/
• https://www.wikiwand.com/en/Color_difference
• Sharma 2005
• http://www.colorwiki.com/wiki/Delta_E:_The_Color_Difference