What is the correct method for measuring the color contrast of screen elements that are anti-aliasing (especially text but not limited to text)? Is there a standard method at all?
Here is my specific situation: I'm trying to maintain WCAG 2.0 for text in a drop-down menu. An enlarged screenshot of the menu is below:
This is a standard IE11
without a custom style, the text is nominal
# 000080, However, the screenshot clearly shows that the text contains many pixels in different shades of blue and pink due to anti-aliasing. Depending on which pixel I select as foreground, I can achieve such a high contrast 16.0: 1 (pure white on dark blue) at least as low as 2.4: 1 (royal blue on dark blue).
My customer's QA employees say the contrast exists 2,9: 1much lower than the minimum requirement of 4.5: 1, I do not know what your measurement strategy is, and I have no direct connection to them.
What I want to do now is to find the right way to measure this, so that I can at least tell my customer-facing team members that we are doing it right and hopefully working towards a long-term solution.
The problem is that I do not know what counts as "right". My googling has led to many definitions of contrast and explanations why it matters, but nothing about the right way to measure it. Should I choose the pixel with the highest contrast I can find? Pixels with the lowest contrast? Measure a handful of pixels and average the results? Are you using a selector that captures multiple pixels at once? How do I know that I measured the "true" color contrast value in a given situation?