Quantize an image using an existing color palette

Quantize image colors by mapping all pixels to the nearest color in RGB space, respectively, given an arbitrary palette.

image_quantmap(
  file,
  pal,
  pal2 = NULL,
  k = 100,
  plot = FALSE,
  show_pal = TRUE,
  labels = TRUE,
  label_size = 1,
  label_color = "#000000",
  keep_asp = TRUE
)

Arguments

file

if character, file path or URL to an image. You can also provide an RGB array from an already loaded image file.

pal

character, vector of hex colors, the color palette used to quantize the image colors.

pal2

character, optional vector of hex colors, same length as pal. After quantizing image to pal, you can subsequently remap pal to pal2.

k

integer, the number of k-means cluster centers to consider in the image. See details.

plot

logical, plot the palette with quantized image reference thumbnail. If FALSE, only return the RGB array.

show_pal

logical, show the palette like with image_pal(). If FALSE, plot only the image; all subsequent arguments ignored.

labels

logical, show hex color values in plot.

label_size

numeric, label size in plot.

label_color

text label color.

keep_asp

logical, adjust rectangles in plot to use the image aspect ratio.

Value

an RGB array with values ranging from 0 to 1

Details

The palette pal does not need to be related to the image colors. Each pixel will be assigned to whichever color in pal that it is nearest to in RGB space. You can use pal2 to remap to arbitrary colors after quantizing. This function returns the new RGB array. You can plot a preview just like with image_pal() using plot = TRUE. The number of k-means centers k is for binning image colors prior to mapping the palette pal. It is limited by the number of unique colors in the image. Larger k provides more binned distances between image colors and palette colors, but takes longer to run.

See also

image_pal()

Examples

x <- system.file("blue-yellow.jpg", package = "imgpalr")
pal <- c("black", "navyblue", "dodgerblue", "yellow")
pal2 <- c("darkred", "darkgreen", "tomato", "orange")

a <- image_quantmap(x, pal, k = 7, plot = TRUE)

str(a)
#>  num [1:317, 1:400, 1:3] 0 0 0 0 0 0 0 0 0 0 ...

a <- image_quantmap(x, pal, pal2, k = 7, plot = TRUE)