Princeton University

Cornell University

Cornell University

Just as pixels have only a limited number of bits, a painter's palette can only represent a limited number of human-distinguishable colors. To counter this limitation, visual artists have used chromaticity as an alternative visual channel to convey variations of luminance. A striking example is Claude Monet's painting Sunrise, which manages to convey the brightness of a rising sun almost exclusively through chromaticity. Similarly, in Cezanne's painting Mardi Gras, cooler chromaticities are used in place of shading to depict Pierrot's outfit.

Color Contrast for Detail Enhancement: In the painting Sunrise by Claude Monet, details of the sun and its reflection on the water are conveyed almost entirely through variations in chromaticity.

Substituting Chromaticity Variations for Tonal Variations: CGM lets us apply the warm-cool gradient in Mardi Gras by Cezanne to a natural image with a similar white outfit.

Chromaticity mapping is widely observed in cinematography to enhance perceived contrast in both brightness and depths. On set, complementary lighting is applied from various angles to shape the scene, while in post-production, colorists adjust hues in shadows and highlights to achieve effects like the iconic 'Teal and Orange' look.

We propose Chromaticity Gradient Mapping, a method for manipualting color contrast in images and videos. We parameterize chromaticity mapping with two controls: gradient curve and adjustment curve. The gradient curve defines the direction of shifts within the chromaticity space, while the adjustment curve controls the magnitude of these shifts as a function of lightness.

Chromaticity Gradient Mapping: The gradient curve defines the direction of shifts within the chromaticity space (A v.s. C), while the adjustment curve controls the magnitude of these shifts as a function of lightness (B v.s. C).

Web User Interface: Users can adjust the contrast with the "Adjustment Curve" tab on the upper left, and the chromaticity gradient with the "Gradient Curve Editor" tab on the lower left. Image is previewed in the middle. Presets and detail level selection is available in the panel on the right.

By filtering the input lightness map, our method can enhance different levels of details through color contrast adjustment. It can also be used for complementary tone mapping when lightness adjustments and chromaticity adjustments are applied at different frequency levels. Please see our paper for more detail.

Detail Manipulation in Chromaticity: Our method allows users to quickly explore chromaticity adjustments by focusing contrast on details at different scales. The top adjustment uses the chosen color gradient to enhance edge contrast, the middle enhances a mix of edge and detail contrast, and the bottom enhances detail contrast. Image credit to @signatureedits.