Asqatasun v4 - RGAA 3.2016 - Rule 3.3.2
Summary
This test consists in checking whether the contrast ratio between text and its background is at least 4.5:1 for the bold, under 14px sized, textual elements
Business description
Criterion
Test
Description
- Le rapport de contraste entre le texte et son arrière-plan est de 4.5:1, au moins ;
- Un mécanisme permet à l’utilisateur d’afficher le texte avec un rapport de contraste de 4.5:1, au moins.
Level
AA
Technical description
Scope
Page
Decision level
Decidable
Algorithm
Selection
Set1
All the textual elements from the DOM with a font-size inferior or equals to 14px and bold
Set2
All the hidden textual elements from the DOM with a font-size inferior or equals to 14px and bold
Set3
All the <img>
tags
Process
Test1
For each element of Set1, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 4.5.
For each element returning false in Test1, if the ALTERNATIVE_CONTRAST_MECHANISM is set to true by the user, raise a MessageA, raise a MessageB instead.
If an element has a contrast ratio that cannot be determined (background defined with an image or a gradient), raise a MessageC
Test2
For each element of Set2, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 4.5.
For each element returning false in Test2, raise a MessageD
MessageA : Bad Contrast
- code : BadContrast
- status: Failed
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
MessageB : Bad Contrast But Alternative Contrast Mechanism Present On Page
- code : BadContrastButAlternativeContrastMechanismOnPage
- status: Pre-Qualified
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
MessageC : Not Treated Background Color
- code : NotTreatedBackgroundColor
- status: Pre-Qualified
- parameter : none
- present in source : no
MessageD : Bad Contrast on Hidden Element
- code : BadContrastHiddenElement
- status: Pre-Qualified
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
Analysis
Not Applicable
No element with a font-size inferior or equals to 14px and bold have been found (Set1 AND Set2 are empty)
Passed
All the elements with a font-size inferior or equals to 14px and bold have a correct ratio and the page contains no images (Test1 returns true for all elements AND Set2 AND Set3 are empty)
Failed
At least one element with a font-size inferior or equals to 14px and bold have an incorrect ratio (Test1 returns false for at least one element)
Pre-qualified
In all other cases
Notes
- By approximation, we consider that 1.2em of the default font size is equivalent to 14 px.
- The background color (
"background"
css property), the font color ("color"
css property), the font size ("font-size"
css property) and the font weight ("font-weight"
css property) are retrieved while fetching the page, through a javacript script. Each html element is parsed to extract these info, as well as its visibility ("display"
css property equals to none or"visibility"
css property equals to hidden) and whether it is a textual node.