colors-accessibility

Table of Contents:

• Introduction
• Overview
• Installation
• Usage
  • Color
    • Input values
    • Conversions
    • Relative luminance
    • Single space representation
    • Color representations
    • Values to dictionary
  • Accessibility processor
    • Contrast ratio
    • WCAG compliant colors representation
• Further improvements

Introduction

This library help to handle different color values inputs in three color spaces: RGB, HSL and HEX. The main functionality is ability to check the contrast between two colors as well adjusting those colors to fit WCAG 2.1 specification.

Overview

This library provides two main features:

• A class Color that represents a color in many possible color spaces. This class provides following functionalities:
  • Validating color values for each color space - using Validator class.
  • Processing (formatting) color values for each color space - changing format of values to list, dictionary, as well as normalizing values in appropriate color spaces.
  • Converting color values between color spaces.
• A class AccessibilityProcessor that provides following functionalities:
  • Calculating contrast ratio between two colors.
  • Checking if the contrast between two colors has ratio big enough for levels AA and AAA, with ration 4.5:1 and 7:1 respectively.
  • Calculating and getting color that is AA or AAA level of contrast with the given color - by changing either foreground color, background color or both.

Installation

To install colors-accessibility library, run the following command:

pip install colors-accessibility

color-accessibility library does not have any dependencies.

Usage

Color

Color class currently handles three color spaces: rgb, hsl, and hex. This class can process different type of input values. To initialize a color, following inputs are valid:

Input values

For rgb color space:

Code

from colors_accessibility import Color


# All representations below are valid and will be processed correctly.
valid_rgb_representations = [
 [100, 20, 50], ['100', 20, 50], ['100', '20', '50'], {'red': 200, 'green': 20, 'blue': 50},
 {'r': '50', 'g': 0.2, 'b': 100}
]

colors = [
  Color('rgb', representation) for representation in valid_rgb_representations
]

For hex color space:

Code

from colors_accessibility import Color


# All representations below are valid and will be processed correctly.
valid_hex_representations = [
 '1ad', '#1ad', '1ac4bb', '#1ac4bb', ['1ad'], ['#11aabb'],
  {'hex': '1ac4ba'}
]

colors = [
  Color('hex', representation) for representation in valid_hex_representations
]

For hsl color space:

Code

from colors_accessibility import Color


# All representations below are valid and will be processed correctly.
valid_hsl_representations = [
 [120, 0.1, 0.2], ['120', 20, 0.1], ['120', '20', '0.1'],
 {'hue': '0.89', 'saturation': 20, 'lightness': '0.1'}
]

colors = [
  Color('hsl', representation) for representation in valid_hsl_representations
]

Conversions

Color class provides functionality of converting between rgb, hsl and hex color spaces. We can both calculate color values in different color space an

Code

from colors_accessibility import Color


color = Color('rgb', {'red': 170, 'green': 0.23, 'blue': 0})
print(color)

# Calculate coordinates in different color spaces:

hex_color_values = color.to_hex()
print(hex_color_values)

hsl_color_values = color.to_hsl()
print(hsl_color_values)

# Set color to different color space:
color.set_to('hex')
print(color)

Relative luminance

We also have an ability to calculate relative luminance of a color.

Code

from colors_accessibility import Color


color = Color('rgb', {'red': 170, 'green': 0.23, 'blue': 0})

relative_luminance = color.relative_luminance()
print(relative_luminance)

Single space representation

We can get color representations for the specified color. We can choose from: rgb, hsl, hex and all. With all we get representation for all three color spaces.

Code

from colors_accessibility import Color


color = Color('rgb', [120, 53, 89])
print(color)

representation = color.get_representations('hex')
print(representation

Color representations

Here we get the representations for all three spaces.

Code

from colors_accessibility import Color


color = Color('rgb', [120, 53, 89])
print(color)

representation = color.get_representations('all')

print(representation.rgb)
print(representation.hex)
print(representation.hsl)

Values to dictionary

We can format the color representation to a dictionary.

Code

from colors_accessibility import Color


color = Color('rgb', [120, 50, 0.3])
print(color.color_values)

values_dictionary_representations = color.to_dict()
print(values_dictionary_representations)

Accessibility processor

Contrast ratio

We can calculate contrast ratio of a color.

Code

from colors_accessibility import Color


rgb_color = Color('rgb', [120, 53, 89])
hex_color = Color('hex', '#783957')

processor = AccessibilityProcessor(rgb_color, hex_color)
print(processor)

rgb_luminance, hex_luminance = processor.get_luminance_values(
  processor.foreground_color,
  processor.background_color
)
print(rgb_luminance)
print(hex_luminance)

constrast = processor.calculate_contrast(rgb_luminance, hex_luminance)
print(contrast)

WCAG compliant colors representation

We can get the WCAG compliant colors representation - we get them by tweaking HSL color values till contrast between the two input colors are on adequate levels.

Code

from colors_accessibility import AccessibilityProcessor, Color
from pprint import pprint


rgb_color = Color('rgb', [120, 198, 73])
hex_color = Color('hex', '#783957')

processor = AccessibilityProcessor(rgb_color, hex_color)
wcag_compliant_colors = processor.get_all_wcag_compliant_color()
pprint(wcag_compliant_colors.get('lightness').get('background'))

Further improvements

Here are some of the planned further improvements:

• Add ability to get color representations for more color spaces
• Refactor the code
• Add methods to print color representations
• Add methods for easier getting well formatted color representations
• Add more tests to increase the coverage