pnm

0th

Percentile

Reading and writing of bitmap images in PBM (black/white), PGM (grey) and PPM (color) format.

Keywords
file, color
Usage
read.pnm(file, ...)
write.pnm(object, file= NULL, forceplain = FALSE, type = NULL, maxval = 255)
Arguments
file
name of the pnm file (general connections do not work at the moment).
...
further arguments passed to pixmap (like bbox).
object
an object of class "pixmap".
forceplain
logical; if true, an ASCII pnm file is written. Default is to write a binary (raw) file.
type
one of "pbm", "pgm" or "ppm". Default is to use "pgm" for grey images and "ppm" for color images.
maxval
the maximum color-component value; the default is a colour depth of 8 bits, i.e., the integer 255.
Details

read.pnm reads a pnm file and loads the image into an object of class pixmap.

write.pnm writes an object of class pixmap to a pnm file, the type argument controls wheter the written image file is a black-and-white bitmap (pbm), grey (pgm) or color (ppm).

plot.pnm plots a pnm object using the command image. The only difference is that the element [1,1] of pnmobj is plotted as the upper left corner (plain image would plot [1,1] as the lower left corner.

Value

read.pnm returns an object of class pixmapRGB for color pixmaps (ppm), and an object of class pixmapGrey for pbm and pgm. Note that the type of file as determined by the first two bytes according to pnm standards is important, not the extension of the file. In fact, the file name extension is completely ignored.

pixmap

• write.pnm
Examples
 x <- read.pnm(system.file("pictures/logo.ppm", package="pixmap")[1])
plot(x)
print(x)