plotPixels {colordistance}

Plot pixels in color space

Description

Plots non-background pixels according to their color coordinates, and colors them according to their RGB or HSV values. Dimensions are either RGB or HSV depending on flags.

Usage

plotPixels(
  img,
  n = 10000,
  lower = c(0, 0.55, 0),
  upper = c(0.25, 1, 0.25),
  color.space = "rgb",
  ref.white = NULL,
  pch = 20,
  main = "default",
  from = "sRGB",
  xlim = "default",
  ylim = "default",
  zlim = "default",
  ...
)

Arguments

img

Either a path to an image or a loadImage object.

n

Number of randomly selected pixels to plot; recommend <20000 for speed. If n exceeds the number of non-background pixels in the image, all pixels are plotted. If n is not numeric, all pixels are plotted.

lower

RGB or HSV triplet specifying the lower bounds for background pixels. Default upper and lower bounds are set to values that work well for a bright green background (RGB [0, 1, 0]).

upper

RGB or HSV triplet specifying the upper bounds for background pixels. Default upper and lower bounds are set to values that work well for a bright green background (RGB [0, 1, 0]). Determining these bounds may take some trial and error, but the following bounds may work for certain common background colors:

• Black: lower=c(0, 0, 0); upper=c(0.1, 0.1, 0.1)

• White: lower=c(0.8, 0.8, 0.8); upper=c(1, 1, 1)

• Green: lower=c(0, 0.55, 0); upper=c(0.24, 1, 0.24)

• Blue: lower=c(0, 0, 0.55); upper=c(0.24, 0.24, 1)

If no background filtering is needed, set bounds to some non-numeric value (NULL, FALSE, "off", etc); any non-numeric value is interpreted as NULL.

color.space

The color space ("rgb", "hsv", or "lab") to use for plotting.

ref.white

The reference white passed to convertColor; must be specified if img does not already contain CIE Lab pixels. See convertColorSpace.

pch

Passed to scatterplot3d.

main

Plot title. If left as "default", image name is used.

from

Original color space of image if plotting in CIE Lab space, probably either "sRGB" or "Apple RGB", depending on your computer.

xlim, ylim, zlim

Ranges for the X, Y, and Z axes. If "default", the widest ranges for each axis according to the specified color space (0-1 for RGB and HSV, 0-100 for L of Lab, -128-127 for a and b of Lab) are used.

...

Optional parameters passed to scatterplot3d.

Value

3D plot of pixels in either RGB or HSV color space, colored according to their color in the image. Uses scatterplot3d function.

Note

If n is not numeric, then all pixels are plotted, but this is not recommended. Unless the image has a low pixel count, it takes much longer, and plotting this many points in the plot window can obscure important details.

There are seven CIE standardized illuminants available in colordistance (A, B, C, E, and D50, D55, and D65), but the most common are:

• "A": Standard incandescent lightbulb

• "D65": Average daylight

• "D50": Direct sunlight

Examples

colordistance::plotPixels(system.file("extdata",
"Heliconius/Heliconius_B/Heliconius_07.jpeg", package="colordistance"),
n=20000, upper=rep(1, 3), lower=rep(0.8, 3), color.space = "rgb", angle = -45)