Large Text Comparison (LTC) bookmarklet

Description

WCAG SC 1.4.3 allows a minimum contrast ratio of 3:1 for “large-scale text”, defined by WCAG as “18 point or 14 point bold.” Unlike html text, where the font size can be programmatically determined, the size of images of text must be ascertained by other means, such as visual comparison.
This bookmarklet creates a box with samples of large-scale text with height comparison (sizing) lines above and below the sample text. The box can be moved onscreen to images of text, to determine if they qualify as large-scale text.

Instructions

1. At the prompt, enter an integer to specify the transparency level (1 = opaque). Pressing OK without entering a value uses the default setting of 2.
2. Drag the box beside or in front of the image of text.
1. Mouse: drag
2. Keyboard: arrow keys
3. Using the regular or bold sample as appropriate, use the sizing lines to see if the image of text is at least the sample size.
4. Use Esc to close the box.