ColorAssim — Color Assimilation Demo
ColorAssim turns a portrait photo into a color assimilation illusion: the same face appears in nine different colors, even though the face pixels are identical in every panel. Curious how that works? The main page explains the science. Below are answers to common questions about using the app.
Solely to take the photo for the demonstration. Everything happens on your device: the photo is processed locally, is never uploaded anywhere, and is discarded when you close the app. There are no accounts, no ads, and no tracking — see the privacy policy for details.
If you denied camera access and want to enable it later: on iPhone/iPad, go to Settings → Privacy & Security → Camera and switch on ColorAssim. On Android, long-press the app icon → App info → Permissions → Camera.
Face the camera straight on in even light, and fit the oval snugly around the face — drag to move it, pinch to resize, or use the sliders for fine-tuning. The tighter the oval hugs the face, the more striking the illusion.
The app normally finds the person in the photo automatically. If it can’t — for example with pets, statues, or objects — it asks whether to use the oval region as-is. Adjust the oval so it closely surrounds your subject, then choose Use Oval Anyway. That is the trick for cats, dogs, and anything else with a face.
No — and the app lets you prove it. Tap the result image and the stripes covering the face fade away: the face underneath is identical in all nine panels. Pinch to zoom in on any detail and tap again while zoomed — the pixels never change, only your perception of them. Double-tap to zoom back out.
Tap = toggle the stripes · pinch = zoom · double-tap = reset zoom
On iPhone and iPad, in your Photos library. On Android, in your gallery under Pictures / ColorAssim. Saving and sharing always use the view currently on screen — so you can save the image twice, once with stripes and once without, by tapping the image in between.
iPhone and iPad with iOS 17 or later, and Android phones and tablets with Android 8.0 or later. A camera is required.
Email gegenfurtner@me.com and include your device model, system version, and what you expected to happen. Bug reports and ideas are very welcome — this app exists to share a beautiful piece of vision science.