color.py

Sub-module providing color functions.

References,

• https://en.wikipedia.org/wiki/Color_difference

• http://www.easyrgb.com/en/math.php

• Measuring Colour by R.W.G. Hunt and M.R. Pointer

rgb_to_xyz(red, green, blue)

Convert standard RGB color to XYZ color.

D65/2° standard illuminant.

Parameters:

• red (int) – RGB value of Red.

• green (int) – RGB value of Green.

• blue (int) – RGB value of Blue.

Returns:

Tuple (X, Y, Z) representing XYZ color

Return type:

tuple

xyz_to_lab(x_val, y_val, z_val)

Convert XYZ color to CIE-Lab color.

Parameters:

• x_val (float) – XYZ value of X.

• y_val (float) – XYZ value of Y.

• z_val (float) – XYZ value of Z.

Returns:

Tuple (L, a, b) representing CIE-Lab color

Return type:

tuple D65/2° standard illuminant

rgb_to_lab(red, green, blue)

Convert RGB color to CIE-Lab color.

Parameters:

• red (int) – RGB value of Red.

• green (int) – RGB value of Green.

• blue (int) – RGB value of Blue.

Returns:

Tuple (L, a, b) representing CIE-Lab color

Return type:

tuple D65/2° standard illuminant

dist_rgb(rgb1, rgb2)

Determine distance between two rgb colors.

Parameters:

• rgb1 (tuple) – RGB color definition

• rgb2 (tuple) – RGB color definition

Returns:

Square of the distance between provided colors

Return type:

float

This works by treating RGB colors as coordinates in three dimensional space and finding the closest point within the configured color range using the formula:

d^2 = (r2 - r1)^2 + (g2 - g1)^2 + (b2 - b1)^2

For efficiency, the square of the distance is returned which is sufficient for comparisons

dist_rgb_weighted(rgb1, rgb2)

Determine the weighted distance between two rgb colors.

Parameters:

• rgb1 (tuple) – RGB color definition

• rgb2 (tuple) – RGB color definition

Returns:

Square of the distance between provided colors

Return type:

float Similar to a standard distance formula, the values are weighted to approximate human perception of color differences For efficiency, the square of the distance is returned which is sufficient for comparisons

dist_cie76(rgb1, rgb2)

Determine distance between two rgb colors using the CIE94 algorithm.

Parameters:

• rgb1 (tuple) – RGB color definition

• rgb2 (tuple) – RGB color definition

Returns:

Square of the distance between provided colors

Return type:

float For efficiency, the square of the distance is returned which is sufficient for comparisons

dist_cie94(rgb1, rgb2)

Determine distance between two rgb colors using the CIE94 algorithm.

Parameters:

• rgb1 (tuple) – RGB color definition

• rgb2 (tuple) – RGB color definition

Returns:

Square of the distance between provided colors

Return type:

float For efficiency, the square of the distance is returned which is sufficient for comparisons

dist_cie2000(rgb1, rgb2)

Determine distance between two rgb colors using the CIE2000 algorithm.

Parameters:

• rgb1 (tuple) – RGB color definition

• rgb2 (tuple) – RGB color definition

Returns:

Square of the distance between provided colors

Return type:

float For efficiency, the square of the distance is returned which is sufficient for comparisons