plot_pixels: Plot the pixels of a transformed image
In ropensci/pixelclasser: Classifies Image Pixels by Colour

Description Usage Arguments Details Value See Also Examples

This function is a wrapper for function points() in package graphics for plotting the pixels of a transformed rgb image on the triangular diagram previously created by plot_rgb_plane().

1	plot_pixels(image_rgb, x_axis, y_axis, ...)

`image_rgb`	an object produced by `read_image()`.
`x_axis`	a character string indicating which colour variable use as x.
`y_axis`	a character string indicating which colour variable use as y.
`...`	additional graphical parameters, mainly to set the colour (`col`) of the points.

It is advantageous to specify a colour such as "#00000005" which is black but almost transparent. In this way a kind of density plot is created because the clustering of points creates areas of darker colour. Note that a colour without specific transparency information defaults to an opaque colour, so "#000000" is the same as "#000000ff". The colours can be specified in any form understandable by grDevices::col2rgb, but the hexadecimal string allows setting the colour transparency and it is the preferred style. Note also that the points are plotted using pch = ".", as any other symbol would clutter the graph.

Warning: plotting several million points in an R graph is a slow process. Be patient or reduce the size of the images as much as possible. Having a nice smartphone with a petapixel camera sensor is good for artistic purposes, but not always for efficient scientific work.

The function does not return any value.

plot_rgb_plane, col2rgb

# Plotting the pixels of the example image included in this package
ivy_oak_rgb <- read_image(system.file("extdata", "IvyOak400x300.JPG",
                                       package = "pixelclasser"))
plot_rgb_plane("g", "b")
plot_pixels(ivy_oak_rgb, "g", "b", col = "#00000005")