WCAG Failure: Color contrast of thumbnail text on thumbnail is too low

[patdunlavey]

From an accessibility audit of our Mirador 3 install:

• Failed WCAG Success Criteria: 1.4.3 Contrast (Minimum) (AA)
• Color contrast of thumbnail text on thumbnail is too low at 4:1 vs. 4.5:1 required.

Recommendation: Use a darker gray on the thumbnail text.

[lhenze]

Hi there, looking at this in the context of Mirador 4 -- what I see is white text on top of each image now. Am I looking in the right place? If so, yes, this is still an issue, because the background of the text is transparent, and so the contrast can't be predicted.

[lhenze]

To amend this a bit, there is a now gradient behind the text. If I put an all-white image in the thumbnail, the pixels for the background read as #AAAAAA at the top, which set behind white text provides a 2.32 contrast. So the gradient helps a lot but it's still potentially below the required contrast.

Here's what it would look like with gradient removed at background set at #757575, providing 4.61 contrast.

Thoughts on this, other design ideas?