pnm: Read/Write Portable Anymap Images

In pixmap: Bitmap Images / Pixel Maps

Description

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

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.

Author(s)

Roger Bivand and Friedrich Leisch

See Also

pixmap

Examples

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

 x <- read.pnm(system.file("pictures/logo.pgm", package="pixmap")[1])
 plot(x)

 x <- read.pnm(system.file("pictures/logo.pbm", package="pixmap")[1])
 plot(x)

Example output

Warning message:
In rep(cellres, length = 2) : 'x' is NULL so the result will be NULL
Pixmap image
  Type          : pixmapRGB 
  Size          : 77x101 
  Resolution    : 1x1 
  Bounding box  : 0 0 101 77 

Warning message:
In rep(cellres, length = 2) : 'x' is NULL so the result will be NULL
Warning message:
In rep(cellres, length = 2) : 'x' is NULL so the result will be NULL

pixmap documentation built on Jan. 29, 2021, 5:08 p.m.