Black on white: reproduce the maximum 21:1 contrast ratio
Calculate #000000 against #FFFFFF and connect channel values, luminance, ratio and all five displayed references.
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ContrastCheck examples with reproducible hex inputs
Follow black on white to exactly 21:1, then compare #777777 and #767676 on white around the 4.5:1 boundary.
#777777 versus #767676 on white: why one fails AA normal text
Reproduce two nearby gray values whose raw ratios fall on opposite sides of the 4.5:1 normal-text threshold.
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