Good visual contrast is essential for readability. It allows readers, including those with visual impairments, to easily distinguish text and images from the background.

Objectives

• Allow a good readability of the content.
• Limit cognitive load during consultation.
• Improve accessibility of content to readers with disabilities.

Implementation

• Ensure a minimum contrast ratio of 3:1 between text and background, as measured via WCAG2.0 algorithm

Control

• Either upstream (at the time of the design of the digital book) : Repeating contents whose contrast/luminosite difference with their background is potentially insufficient; Use a tool like Colour Contrast Analyzer to calculate the contrast ratio : click on LuminoSitee and raise the color of the foreground and then that of the second plane in the defined fields; Make sure the contrast ratio is higher or equal to 3:1
• Either downstream : Use ACE and its error report. Please check the case in the “Errors” tab and search for “color-contract”. Follow the procedure described above.