Module contrast 

Contrast ratios between tones, and tones that reach a given ratio.

The safe functions return None where upstream returns -1.

Functions

darker

A tone at least as dark as tone that reaches ratio, if one exists.

darker_unsafe

darker, or 0 when ratio cannot be reached.

lighter

A tone at least as light as tone that reaches ratio, if one exists.

lighter_unsafe

lighter, or 100 when ratio cannot be reached.

ratio_of_tones

The contrast ratio of two tones, from 1 to 21. Tones are clamped to 0..=100.

ratio_of_ys

The contrast ratio of two relative luminances.