Rvision (version 0.6.0)

imhist: Multichannel Histogram of an Image

Description

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

Usage

imhist(
  image,
  nbins = 256,
  range = c(0, 255),
  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.

See Also

Image

Examples

# NOT RUN {
balloon <- image(system.file("sample_img/balloon1.png", package = "Rvision"))
imhist(balloon, plot = TRUE)

# }