Version 5.1 mainly introduces a new, graphical interface:
FEATURE: The textual menu was replaced by a graphical menu to make the extension easier to use and more flexible.
FEATURE: The lightness inversion options that relied on brightness estimation were removed become of errors in drawWindow.
FEATURE: Two CSS color properties were added: "border-image-source" and "outline-color".
FEATURE: Two options were added to control the automatic coloration of pages at web domains for which a theme index was saved.
FEATURE: An option was added to make foreground images less opaque (except on hover) to reduce contrast with dark backgrounds.
FEATURE: An option was added to enable delaying the first paint event to make it more likely that the page shows up colorized.
FEATURE: An option was added to enable making all element borders transparent so as to impose a 'flat' design.
FIX: The maximum image size limits were increased to prevent downsizing or exclusion of images when this is not desired/necessary.
FIX: An error in the low-level transform which led to noticable hue shifts was corrected.
FIX: In the HSL-to-RGB transform, the saturation (g) is now set to 0 when it is negative to prevent underflow.
CODE: The hsl transform in 'cta.js' was sped up by 40% by replacing the array of transform coefficients by named constants.
CODE: Instead of repeated calls to garbageCollect, forceGC() is now called once after the main document is transformed.