Is the von Kries correction on this page real math?

Yes. Each patch's true reflectance is multiplied by the illuminant's own RGB to produce the tinted appearance, and the Adaptation Strength slider blends that result toward the reflectance divided back out by the same illuminant — an exact per-channel implementation of the von Kries transform, not a scripted animation.

How is Retinex mode different from ordinary adaptation?

Retinex mode normalises each colour channel by dividing it by that channel's own maximum value across the scene. Because a scene-wide illuminant multiplies every channel by a constant, that constant cancels in the ratio — the mode shows the same normalised value under a neutral light and a warm light, proving colour perception depends on reflectance ratios, not absolute intensity.

Why does the Dress Illusion mode show two different results from the same base pixel?

The same ambiguous base colour is run through von Kries division by two different assumed illuminants — a bright warm one and a dim cool one. Discounting the warm illuminant yields blue/black, discounting the cool one yields white/gold, mirroring the two competing readings people reported for the real photograph.

Home▸Perception & Optical Illusions▸Color Constancy & Chromatic Adaptation (2D)

Color Constancy & Chromatic Adaptation (2D)

A Canvas2D von Kries chromatic-adaptation lab: divide RGB channels by an illuminant estimate to restore true reflectance, plus Simultaneous Contrast, Dress Illusion and Retinex normalisation views.

Perception & Optical Illusions2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

This 2D companion renders the same von Kries chromatic-adaptation math as the 3D version through plain Canvas2D fills instead of a fragment shader: nine reference patches sit under a tinted illuminant, an Adaptation Strength slider blends each patch's colour back toward its true reflectance by dividing out the illuminant per channel, and dedicated Simultaneous Contrast, Dress Illusion and Retinex-normalisation views sit behind the same Display Mode selector as the 3D original.

⚙ Under the hood

Canvas2D von Kries chromatic adaptation: per-channel divide-by-illuminant blended by an adaptation-strength slider, with Simultaneous Contrast, Dress Illusion and Retinex reflectance-ratio modes.

color constancychromatic adaptationvon kriesretinexcolor perception2d

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install