Optical Illusion

Luminance-gradient-dependent lightness illusion

submitted by Colin Fay

This animation is an example of a “gradient illusion”, which is an illustration of how the perception of a color is influenced by the surrounding of this color.

When looking at the animation, we perceive the color in the square as changing (from darker to lighter), when in fact it stays the same (as you can see, the fill is argument is always #7E7E7E).

The Code

# Coordinates for 10 squares
d <- data.frame(
  x1 = 1:10, x2 = 2:11,
  y1 = 4, y2 = 5,
  t = 1:10
)

# Creating the gradient background
library(grid)
g <- rasterGrob(
  t(colorRampPalette(c("#000000", "#FFFFFF"))(1000)),
  width = unit(1, "npc"), height = unit(1, "npc")
)

# Creating the animation
library(ggplot2)
library(ggmap) # For theme_nothing()
library(gganimate)
ggplot() +
  annotation_custom(g, -Inf, Inf, -Inf, Inf) +
  geom_rect(
    data = d,
    mapping = aes(xmin = x1, xmax = x2, ymin = y1, ymax = y2),
    color = "black", fill = "#7E7E7E"
  ) +
  ylim(c(1, 8)) +
  theme_nothing() +
  transition_time(t)

Source

Remaking ‘Luminance-gradient-dependent lightness illusion’ with R