How to check text contrast over AI images

To check text contrast over AI images, test the text against the part of the background directly beneath it in every layout. Start with the narrowest crop, where the headline is most likely to wrap or land on a highlight. Keep the words editable, then move them, shade the image locally or give them a solid background. Check again with the actual copy and font in place.

Set a contrast target for the type

For web content, W3C’s explanation of WCAG 2.2 Level AA gives a minimum contrast ratio of 4.5:1 for ordinary text and 3:1 for text that qualifies as large. A heading style alone does not make the text large: check its rendered size and weight. A short label below the headline may still need 4.5:1. Treat the threshold as a floor. If a design sits right on the line, extra contrast can make it easier to read at a glance.

Measure the background the letters actually cover

Imagine a ceramics workshop banner with a pale vase on the right and a dark blue wall on the left. On desktop, a white headline sits entirely over blue. On a shorter mobile crop, the image shifts and the last line crosses a tan patch of sunlight. A whole-image average would miss that patch. In a preview at the intended size, temporarily hide the text while keeping the image and any overlay in place. Sample the background behind the words, especially the brightest spots under white letters. Use the intended text color in the contrast calculation instead of a partially smoothed edge pixel.

Compare the strongest and weakest spots

These example values illustrate the difference: solid white against dark blue #253343 gives about 12.86:1, and white against tan #B9A78E gives about 2.34:1. They are example colors, not samples from the cover. The dark area easily clears the ordinary-text threshold. The tan patch falls below both benchmarks. Read the whole line at its delivered size and check the lowest ratio where letters appear. If the background has busy edges or texture, sample more than one point in those areas.

Pick a fix that holds up across crops

First try moving the headline into a stable area of the image, while leaving enough space for a longer translation. If the image must fill the layout, a local gradient can darken the area behind the words without dimming the vase. Measure at the weakest point after applying it. If the text moves between crops or the image rotates frequently, use a solid panel or put the text outside the image. White on a solid #222222 panel gives about 15.91:1. The trade-off is that the panel covers part of the photograph, so leave room for it in the composition.

Repeat the check with the delivered layout

Preview the widest and narrowest layouts, a longer translation, and any supporting text that wraps under the title. Keep the headline as editable foreground text for future revisions. Save the crop and overlay settings with the approved design. See W3C’s explanation and technique G18 for the contrast method, Tong’s guide to campaign crops for planning crop geometry, and Tong Academy for other image workflows.