Mathematica Import/Export Format

PGM (.pgm)

MIME type: image/x-portable-graymap
PGM grayscale raster image format.
Member of the Portable family of image formats.
Related to PBM and PPM.
Implements a subset of the PNM format.
Native format of the Netpbm graphics software package.
Primarily used as an intermediate file format on Unix systems.
PGM is an acronym for Portable Gray Map.
ASCII or binary format.
Stores raster images formatted as plain text, representing each pixel as an 8-bit gray level.
Developed in 1988 as part of the Pbmplus package.

Import and Export fully support the PGM format.

Export creates binary PGM files.

If multiple images are present in a PGM file, Import returns the first of the images.

IMPORT AND EXPORT

Import["file.pgm"] imports a PGM file, returning a graphics object.

Export["file.pgm", expr] exports graphics or any other expression as a PGM raster image.

Export by default generates binary PGM files.

Import["file.pgm"] returns an expression of the form Graphics[Raster[data], opts], where data is an array of gray-level values.

Export["file.pgm", expr] creates a PGM image with the same image size as the displayed form of .

Because PGM is a raster image format, all fonts are rasterized on export.

Import["file.pgm", elem] imports the specified element from a PGM file.

Import["file.pgm", {elem, sub_a, sub_b, ...}] imports a subelement.

Import["file.pgm", {{elem₁, elem₂, ...}}] imports multiple elements.

The import format can be specified with Import["file", "PGM"] or Import["file", {"PGM", elem, ...}].

Export["file.pgm", expr, elem] creates a PGM file by treating expr as specifying element elem.

Export["file.pgm", {expr₁, expr₂, ...}, {{elem₁, elem₂, ...}}] treats each expr_i as specifying the corresponding elem_i.

Export["file.pgm", expr, opt₁->val₁, ...] exports expr with the specified option elements taken to have the specified values.

Export["file.pgm", {elem₁->expr₁, elem₂->expr₂, ...}, "Rules"] uses rules to specify the elements to be exported.

See the reference pages for full general information on Import and Export.

ImportString and ExportString support the PGM format.

NOTEBOOK INTERFACE

In the notebook front end, Insert ► Picture and the Open menu allow import of a PGM file into a cell.

Save Selection As exports the selected part of a notebook as a PGM file.

ELEMENTS

General Import elements:

	"Elements"	list of elements and options available in this file
	"Rules"	full list of rules for each element and option
	"Options"	list of rules for options, properties and settings

Data representation elements:

	"Data"	array of grayscale values
	"Graphics"	Graphics object representing an image
	"GrayLevels"	equivalent to "Data"
	"RGBColorArray"	array of RGBColor objects

Import and Export by default use the "Graphics" element for PGM files.

Advanced Import element:

"ImageSize"

raster dimensions

OPTIONS

General option:

ImageSize

Automatic

overall image size

Import options:

	"ColorMap"	None	determines the grayscale palette used for representing the imported PGM
	"DitheringMethod"	"FloydSteinberg"	the dithering method used when color reduction is performed on Import

The following settings can be given for "ColorMap":

	Automatic	chooses an adaptive set of at most 256 colors
	n	adaptive set of at most n colors
	{color₁, color₂, ...}	list of GrayLevel objects
	None	no color reduction is performed

The "DitheringMethod" option specifies the dithering algorithm used for generating the color-reduction palette on Import:

	"FloydSteinberg"	Floyd-Steinberg error diffusion dithering
	None	no dithering is used

Export option:

"ImageTopOrientation"

Top

orientation of the exported image

Detailed property:

"ColorSpace"

GrayLevel

color space of the image

TUTORIALS

Importing Graphics and Sounds

Exporting Graphics and Sounds