Re: contrast for images of text

Oops! You are right, I mixed this with SC 1.3.1... In any case, the 
technique about "distinguising links" is clearly a reference to 
contrast, not "color vision". If we simply use shades of gray there is 
no difference between someone with color deficiencies and someone with 
perfect vision.

Adam clarified:

> If I understand you correctly, the programmatic determination (role, 
> alt, etc.) would satisfy 1.4.1. I am not sure of that. Since 1.4.1 is 
> intended among others for visually impaired users, then appropriate 
> markup might not be sufficient. Perhaps a visual cue is needed to 
> augment the use of color, as implied by the techniques for 1.4.1
> 
 > Ramón wrote:
> 
>     I assume that you refer to "images of text with poor contrast". I
>     agree that they would fail 1.4.1 since, for low vision users, the
>     embedded text is conveying the information relying on color alone.
>     Even if the text is provided in an alt text, for example, many low
>     vision users don't rely on screen readers and therefore might miss
>     the information completely.
> 
>     Indeed, I see the technique regarding the "distinguisable links" as
>     a logical interpretation of SC 1.4.1 that implicitly recognises the
>     importance of contrast. Being a "sufficient technique" for SC 1.4.1,
>     it seems to suggest that the contrary would be a failure, although
>     no failure exists to indicate that. Moreover, the technique does not
>     really refer to color, but contrast ratio between links and the
>     surrounding text, which makes me think that it should apply to 1.4.3
>     and not 1.4.1. In fact, the role information is there, so color is
>     obviously not the only way to convey the presence of the link. That
>     said, I think that the technique is properly attached to 1.4.1,
>     because it correctly assumes that not providing contrast is
>     equivalent to relying on colour.
> 
>     I can even imagine a weird situation where the level A is
>     theoretically met, although in practice there is a severe barrier
>     for many users.
> 
>     Imagine the following image of text that acts as a heading for a
>     link "more info":
> 
>     - Text: "Special offer! WiFi router for only $5.99"
> 
>     - Color: light gray (#CCCCCC) over white
> 
>     - Fails 1.4.3 AA (contrast ratio = 1.6:1) and 1.4.5 AA (image of
>     text), maybe fails 1.4.4 also, although it does not refer to "images
>     of text". In any case, it is also AA.
> 
>     - "Pass" 1.3.1, 1.4.1 and 4.1.2 due to the programmatically
>     determinable text included in the @alt, apparently no more "A"
>     criteria involved)
> 
>     Below this image of text we have a link "more info" in normal text,
>     with a gray Color (#717171) over the overall white background.
> 
>     - Pass 1.4.1 (the information of the link itself "more info" does
>     not rely on color, but anyway the contrast ratio with the
>     "surrounding" text is 3.0:1)
> 
>     - Pass 2.4.4 (level A), since the "context" is provided with the
>     image of text (@alt for blind users and the image itself for sighted
>     users, since it passes "A")
> 
>     Thus, we have an image of text that is virtually invisible for
>     anyone that has not a more-than-perfect vision (but passes A), and a
>     link that is perfectly visible and passes level-A because the
>     context is there.
> 
>     The described situation is more or less common, maybe the low
>     contrast is not as critical, but I've seen many "iamge headings"
>     with contrast ratios of 2.0:1 or similar, which are almost invisible
>     for me.
> 
>     Therefore, I think that a technique similar to the "distinguisable
>     links" should be created for images of text that have not enough
>     contrast, and even a pair of failures of SC 1.4.1 due to "relying on
>     color with an insufficient contrast ratio to convey information", or
>     something like that.
> 
>     Kind regards,
>     Ramón.
> 
> 
>

Received on Wednesday, 30 April 2014 09:27:33 UTC