imghist {gdi}

Simple histogram analysis for all color values in an input image. Can be used to help assess whether a chosen threshold value is appropriate for differentiating the silhouette from the background, or for general image analysis purposes.

Description

Simple histogram analysis for all color values in an input image. Can be used to help assess whether a chosen threshold value is appropriate for differentiating the silhouette from the background, or for general image analysis purposes.

Usage

imghist(
  image_file,
  threshold = 0.5,
  channel = 4,
  breaks = seq(0, 1, 0.05),
  plot = TRUE,
  unique = FALSE
)

Arguments

image_file

Image to be read. Images can be jpeg or png files, or a previously read image saved as an object in R.

threshold

Reference value for color criterium after which pixels that are part of the silhouette should be differentiated from the background.

channel

color channel to which to apply the threshold criterium. Default is 4 (alpha channel of rgba image). Channel setting needs to be adjusted depending on the color mode of the image used (e.g. there are two channels to choose from in a greyscale image, and 3 in an rgb image).

breaks

A vector of breaks for the histogram, defaults to a bin width of 0.05 between color values of 0 and 1.

plot

Whether to plot a histogram, defaults to TRUE

unique

Whether to return counts for unique color values, defaults to FALSE.

Value

A plotted histogram (unless plot==FALSE), and a matrix containing the counts from the histogram (default) or the counts for unique color values (if unique==TRUE).

Examples

fdir <- system.file(package="gdi")
imghist(file.path(fdir,"exdata","lat.png"))