Input of a colour value (in Hexadecimal format) into a text box.Note: This feature was inspired by the Color Palette Creator. This pallet is useful for testing lighter and darker shades of the base colour, which may improve the visibility of the colour combination being tested. The bottom row begins at 85% rather than 100% and continues on as the first. The opacity values are 100% opaque, 75%, 50%, 25% and 10% on the top row. The top row emulates opacity over a white background, the bottom over black. The bottom (smaller) colour pallet consists of 10 shades of the currently selected base colour, located top-left, at varying degrees of opacity. Use this to help you test and choose suitable colour combinations. Colour pallet(s) accessed via a select box.The Colour Choice controls are divided into 2 sections (foreground & background) each has 3 ways to choose a colour to test. The user interface consists of 4 sections WCAG 1.0 requires that "foreground and background colour combinations provide sufficient contrast when viewed by someone having colour deficits, or when viewed on a black and white screen." Use the CCA to test colour combinations against the W3C's suggested algorithm for determining "sufficient contrast". Assessing conformance with Checkpoint 2.2 of the Web Content Accessibility Guidelines 1.0
The Colour Contrast Analyser ( CCA) is useful to help determine, in particular, the legibility of text on a web page and the legibility of image based representations of text. The difference between the background colour and the foreground colour should be greater than 500. (maximum (Red value 1, Red value 2) - minimum (Red value 1, Red value 2)) + (maximum (Green value 1, Green value 2) - minimum (Green value 1, Green value 2)) + (maximum (Blue value 1, Blue value 2) - minimum (Blue value 1, Blue value 2)) Colour Difference FormulaĬolour difference is determined by the following formula: This brightness value gives a perceived brightness for a colour. Note: This algorithm is taken from a formula for converting RGB values to YIQ values. The difference between the background brightness, and the foreground brightness should be greater than 125. Colour Brightness FormulaĬolour brightness is determined by the following formula:
#Colour contrast analyser verification
Note: Hewlett Packard (HP) provide an online colour contrast verification tool that uses the W3C algorithms, but sets the Colour Difference range at > 400, which results in a greater range of foreground & background colour combinations being deemed acceptable. " Two colours are considered to provide good colour visibility if the brightness difference and the colour difference between the two colours are greater than a set range." The range suggested by the W3C is > 125 for colour brightness and > 500 for colour difference. Determining "colour visibility" is based on algorithms suggested by the World Wide Web Consortium (W3C): It is a tool for checking foreground & background colour combinations to determine if they provide good colour visibility.
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