scale_image: Image color scales
In joelcarlson/RImagePalette: Extract the Colors from Images

Description Usage Arguments Details See Also Examples

Uses the image color scale.

scale_color_image(..., image, n = 3, choice = mean, volume = FALSE,
  discrete = TRUE)

scale_colour_image(..., image, n = 3, choice = mean, volume = FALSE,
  discrete = TRUE)

scale_fill_image(..., image, n = 3, choice = mean, volume = FALSE,
  discrete = TRUE)

`...`	parameters to `discrete_scale` or `scale_fill_gradientn`
`image`	Matrix The image from which the palette will be extracted from. Should be a 3 (or more) dimensional matrix. The output of a function such as `readJPG()` or `readPNG()` are suitable as `image`.
`n`	For continuous color scales, you may optionally pass in an integer, n. This allows some control over the scale, if n is too large the scale has too many colors and ceases to be meaningul. n = 3 to n = 5 is recommended.
`choice`	Function Defines how the color will be chosen from the final color cubes. The default choice is to take the `mean` value of the image cube, but other choices may return a subjectively superior scale. Try `median`, or `min`, or `max`, or whatever summary statistic suits your fancy.
`volume`	Logical volume controls the method for choosing which color cube to split at each iteration of the algorithm. The default choice (when `volume = FALSE`) is to choose the cube which contains the largest extent (that is, the largest range of some color). When `volume = TRUE`, the cube with the largest volume is chosen to split. Occasionally, setting to `TRUE` returns a better palette.
`discrete`	generate a discrete palette? (default: `FALSE` - generate continuous palette)

For discrete == TRUE (the default) the function will return a discrete_scale with the plot-computed number of colors. All other arguments are as to scale_fill_gradientn or scale_color_gradientn.

See image_palette for more information on the color scale.

median_cut image_palette vbox display_image

library(ggplot2)

# ripped from the pages of ggplot2
your_image <- jpeg::readJPEG(system.file("img", "Rlogo.jpg", package="jpeg"))
display_image(your_image)

#Discrete scale example
p <- ggplot(mtcars, aes(wt, mpg))
p + geom_point(size=4, aes(colour = factor(cyl))) +
    scale_color_image(image = your_image) +
    theme_bw()

#Continuous scale example
dsub <- subset(diamonds, x > 5 & x < 6 & y > 5 & y < 6)
dsub$diff <- with(dsub, sqrt(abs(x-y))* sign(x-y))
d <- ggplot(dsub, aes(x, y, colour=diff)) + geom_point()
d + scale_color_image(image = your_image, discrete=FALSE) + theme_bw()