colorutils

A library which provides utilities for working with colors in Python. Colors are modeled by the Color class and can be represented in RGB, HEX, WEB, and YIQ formats.

0. Installation

colorutils can be installed from pypi:

pip install colorutils

to update an existing installation from pypi to the latest version:

pip install colorutils --upgrade

1. Current Features

v0.2.1 (released 05/25/2015)

• Bug fix for pip install on Windows for unfound packages

v0.2 (released 05/23/2015)

• Add HSV color representation and conversions
• Add YIQ color representation and conversions
• Color objects can be treated as iterables
• Implementation of color runs
• Addition of pre-defined color palettes
• Package restructuring

v0.1 (released 05/16/2015)

• A versatile abstract color model which allows color addition and subtraction
• Conversions between: RGB tuples, 6-character HEX strings, 3-character HEX strings, and WEB representations of color.
• Random color generation

2. Reporting Bugs / Requesting Features

To report a bug or request a feature for colorutils, please open a new issue

3. Usage

3.1 Instantiating a Color

The basic way to instantiate a Color:

>>> from colorutils import Color
>>> c = Color((255, 255, 255))
>>> c
<Color (255, 255, 255)>

By default, the Color object expects an RGB 3-tuple, but there are multiple ways to instantiate a Color. The possibilities for Cyan, for example:

Color((0, 255, 255))
Color(green=255, blue=255)
Color(rgb=(0, 255, 255))
Color(hex='#00FFFF')
Color(hex='00ffff')
Color(hex='#0ff')
Color(hex='0ff')
Color(web='cyan')
Color(web='Cyan')
Color(web='CYAN')
Color(web='#00ffff')
Color(web='#0ff')
Color(yiq=(0.701, -0.596, -0.217))
Color(hsv=(180, 1, 1))

Color objects can also take the color from other Color objects:

>>> Color(Color((255, 255, 255)))
<Color (255, 255, 255)>

>>> Color(Color(Color(Color((255, 255, 255)))))
<Color (255, 255, 255)>

3.2 Color Conversion

The current color models supported by colorutils are: RGB, HEX, WEB, YIQ, and HSV. Each instantiated Color object has properties which will automatically perform the required conversions:

>>> c = Color((46, 139, 87))

>>> c.red
46

>>> c.green
139

>>> c.blue
87

>>> c.rgb
(46, 139, 87)

>>> c.hex
'#2e8b57'

>>> c.shorthex
'#2e8b57'

>>> c.web
'SeaGreen'

>>> c.yiq
(0.413, -0.152, -0.143)

>>> c.hsv
(146.452, 0.669, 0.545)

If the color were such that the HEX representation could be captured as a 3-char hex:

>>> c = Color((0, 0, 0))

>>> c.hex
'#000000'

>>> c.shorthex
'#000'

The web representation will return the hex value if the color is not a well-known named web color:

>>> c = Color((1, 243, 77))

>>> c.hex
'#01f34d'

>>> c.web
'#01f34d'

These same conversions can be done without instantiating a Color object by using the static methods:

• rgb_to_hex()
• rgb_to_web()
• rgb_to_yiq()
• rgb_to_hsv()
• hex_to_rgb()
• hex_to_web()
• hex_to_yiq()
• hex_to_hsv()
• web_to_rbg()
• web_to_hex()
• web_to_yiq()
• web_to_hsv()
• yiq_to_rgb()
• yiq_to_hex()
• yiq_to_web()
• yiq_to_hsv()
• hsv_to_rgb()
• hsv_to_hex()
• hsv_to_web()
• hsv_to_yiq()

Using these static conversion methods, one can chain conversions (due to the in-param and out-param of all multi-value color representations being a tuple), which you are unable to do using the Python default colorsys.:

>>> rgb_to_hex(hex_to_rgb('#808080'))
'#808080'

Of course, be wary of chaining. Since approximation exists in the conversion algorithms, degradation will occur:

>>> yiq_to_web(rgb_to_yiq(hex_to_rgb('808080')))
'#7f807e'

Though, the values will still be close:

>>> hex(int('80', 16) - int('7f', 16))  # Red difference
'0x1'

>>> hex(int('80', 16) - int('80', 16))  # Green difference
'0x0'

>>> hex(int('80', 16) - int('7e', 16))  # Blue difference
'0x2'

3.3 Color Arithmetic

Although the addition and subtraction of color does not always make sense, the ability to do so is supported. There are two additive models currently supported: LIGHT and BLEND.

3.3.1 Addition

LIGHT

the light model is an additive model, where the rgb components are added, but do not exceed the maximum value, 255. This model is the default model which every Color is initialized with, unless overridden.

An example of LIGHT addition:

>>> Color((0, 100, 200)) + Color((100, 100, 100))
<Color (100, 200, 255)>

BLEND

the blend model is an averaging model, where each rgb component is averaged.

An example of BLEND addition:

>>> Color((0, 100, 200), arithmetic=ArithmeticModel.BLEND) + Color((100, 100, 100))
<Color (50, 150, 250)>

When assigning models, it is important to note that the arithmetic model for the first object in the operation, e.g. Object1 in 'Object1 + Object2', is the model which will be used when computing the addition.

Color addition can also operate on 3-tuples, which represent an RGB value:

>>> Color((50, 50, 50)) + (20, 20, 20)
<Color (70, 70, 70)>

3.3.2 Subtraction

There is currently only one subtractive model, the equivalent to the inverse of the LIGHT additive model. There is no model representing the inverse of BLEND, since the inverse average does not really make sense.:

>>> Color((100, 100, 100)) - Color((0, 75, 200))
<Color (100, 25, 0)>

Color subtraction can also operate on 3-tuples, which represent an RGB value:

>>> Color((50, 50, 50)) - (20, 20, 20)
<Color (30, 30, 30)>

3.4 Color Equality

Testing for equality between colors defaults to testing between the equality of the RGB values:

>>> c1 = Color((10, 20, 30))
>>> c2 = Color((10, 20, 30))
>>> c3 = Color((10, 20, 20))

>>> c1 == c2
True

>>> c1 == c3
False

Different equality functions can be set, using either the predefined equalities in colorutils.equality, or from a custom equality function:

>>> from colorutils.equality import *
>>> c = Color((10, 20, 30), equality_fn=RED_eq)
>>> c2 = Color((10, 40, 60))

>>> c == c2
True

>>> c2 == c
False

Notice that in the above example, when checking for red equality, when the color with the RED_eq equality comes first in the comparison, it evaluates to True. If it comes second, it evaluates to False. This is because the equality function of the first Color instance in the comparison defines which equality function is used.

The predefined equalities are:

• RGB_eq
• RED_eq
• GREEN_eq
• BLUE_eq
• HEX_eq
• WEB_eq
• YIQ_eq
• HSV_eq

Defining a custom equality would follow the pattern defined by the RGB_eq definition, below:

RGB_eq = lambda c1, c2: c1.rgb == c2.rgb

3.5 Color Palettes

A collection of pre-defined color palettes exists for convenience. The palettes which are currently implemented include:

• grayscale
• primary
• rgb
• roygbv
• secondary

Individual named colors can be used from the palettes, or all colors can be retrieved:

>>> import colorutils.palettes.primary as primary

>>> primary.red
<Color (255, 0, 0)>

>>> primary.yellow
<Color (255, 255, 0)>

>>> primary.blue
<Color (0, 0, 255)>

>>> primary.all
[<Color (255, 0, 0)>, <Color (255, 255, 0)>, <Color (0, 0, 255)>]

4. colorutils vs others

To see how the colorutils conversion algorithms compare to other algorithms/provided values, see the comparisons wiki page.