Multichannel Histogram of an Image

imhist computes (or plots) the multichannel histogram of an Image object.

Usage

imhist(
  image,
  nbins = 257,
  range = c(0, 256),
  mask = NULL,
  plot = FALSE,
  col = c("blue", "green", "red", "black"),
  xlab = "Pixel value",
  ylab = "Counts",
  lty = 1,
  ...
)

Arguments

image: An Image object.
nbins: An integer indicating the number of bins of the histogram (default: 256).
range: The range of pixel values to include in the histogram (default: c(0, 256)). The lower boundary is inclusive but the higher one is exclusive.
mask: A single-channel (GRAY) 8-bit (8U) Image object with the same dimensions as image. This can be used to mask out pixels that should not be considered when calculating the histogram (pixels set to 0 in the mask will be ignored during the histogram calculation).
plot: A logical indicating whether to plot the histogram (default: FALSE).
col: A value or vector of any kind of R color specification compatible with col2rgb representing the color of the histogram for each image channel (default: c("blue", "green", "red", "black")).
xlab, ylab: Character strings for the axis labels (default: "Pixel value" for the x axis and "Counts" for the y axis).
lty: A vector of line types, see par.
...: Further arguments passed to matplot.

Value

If plot=FALSE, the function returns a m x n matrix, with m = nbins and n equal to the number of channels in the image + 1. The first column corresponds to the bin values. If plot=TRUE, the function plots the histogram and returned the aforementioned matrix silently.

Author

Simon Garnier, garnier@njit.edu

Examples

balloon <- image(system.file("sample_img/balloon1.png", package = "Rvision"))
imhist(balloon, plot = TRUE)