R: Read/Write Portable Anymap Images

pnm {pixmap} | R Documentation

## Read/Write Portable Anymap Images

### 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)

[Package pixmap version 0.4-11 Index]