Two-color method

(Land-Kuriki method)

since January 7, 2018


"Original image"


Two colorization

"Two-colored image along the red-cyan axis"

For each pixel, values of green and blue are the same.


Two-color transformation (two-color method)

For each pixel, the new color is given as the weighted average between the original cyan and the gray that carries the same value as the original red. Given an original pixel (r, c) and when the weight is 75% for cyan and 25% for red, then the new color is (0.25 r, 0.25 r + 0.75 c), resulting in higher values of cyan. Only when the original pixel is red (100%, 0%), then the new color is gray because the obtained values of red and cyan are the same.

"An image obtained with the two-color method"
(25% for red and 75% for cyan; linear transformation)

For about 80% of observers, strawberries appear to be reddish, though the pixels are not.

Copyright Akiyoshi Kitaoka 2018 (January 7)


"An image obtained with the two-color method"
(50% for red and 50% for cyan; linear transformation)

For some observers, strawberries appear to be reddish, though the pixels are not.

Copyright Akiyoshi Kitaoka 2018 (January 7)


"An image obtained with the two-color method"
(75% for red and 25% for cyan; linear transformation)

For some observers, strawberries appear to be reddish, though the pixels are not.

Copyright Akiyoshi Kitaoka 2018 (January 7)


cf.

"An image obtained with the two-color method"
(100% for red and 0% for cyan; linear transformation)

a gray-scale image

Copyright Akiyoshi Kitaoka 2018 (January 7)


cf.

"An image obtained with the two-color method"
(0% for red and 100% for cyan; linear transformation)

a cyan image without red values

Copyright Akiyoshi Kitaoka 2018 (January 7)



2色法によるイチゴの錯視。この画像はすべてシアン色(青緑色)の画素でできているが、イチゴは赤く見える。

Strawberries appear to be reddish, though the pixels are not. pic.twitter.com/Ginyhf61F7

— Akiyoshi Kitaoka (@AkiyoshiKitaoka) 2017年2月28日


The following image has no red pixels. Do you see the strawberries reddish?

Reference:https://t.co/XbpGfgbMzv

— Akiyoshi Kitaoka (@AkiyoshiKitaoka) 2017年6月26日


Results: In total, eighty-one percent of the reporters saw the strawberries reddish, whereas nineteen percent did not.


With regard to age, there was no statistically significant interaction (χ2 (1) = 2.94, n.s.).


A few squares appear to be bluish, though their pixels are not bluish.



"Illusury light blue"

These photos consist of pixels of red hue, but lines of a train car and a signboard appear to be bluish.

Copyright Akiyoshi Kitaoka 2015 (Janyary 10)



The original photo


Signals appear to be reddish, though they are gray.

Copyright Akiyoshi Kitaoka 2018 (January 7)


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