Netpbm formats

File Format
Name	Netpbm formats
Ontology	Electronic File Formats Graphics Netpbm formats
Extension(s)	.pbm, .pgm, .ppm, .pnm
MIME Type(s)	image/x-portable-anymap, others
PRONOM	fmt/408, others
Released	1988

The Netpbm formats are a family of simple raster image file formats, associated with the Netpbm library and suite of image processing utilities.

The Netpbm formats are often used as "neutral" or "universal" image formats. It's not unusual for an image format's reference software to include a utility to convert to and from one of the Netpbm formats (and perhaps no other formats). Many of these conversion utilities have ultimately been incorporated into the Netpbm software.

Formats

• PBM (portable bitmap) is a bi-level image format.
• PGM (portable graymap) is a grayscale image format.
• PPM (portable pixmap) is a color image format.
• PNM (portable anymap) is a collective name for PBM, PGM, and PPM. A .pnm file may use any of those formats.
• PAM: Refer to PAM (Portable Arbitrary Map). Although PAM is one of the Netpbm formats, it's different enough that it's best documented in a separate article.

Identifiers and Identification

Each file begins with two ASCII characters, which serve as a signature.

The PBM, PGM, and PPM formats come in two varieties: a text (or "plain" or "ASCII") format, and a binary (or "raw") format.

Format	Signature	PRONOM	MIME type
PBM, text	P1	x-fmt/164	image/x-portable-bitmap, image/x-portable-anymap
PBM, binary	P4	fmt/409
PGM, text	P2	fmt/407	image/x-portable-graymap, image/x-portable-anymap
PGM, binary	P5	fmt/406
PPM, text	P3	x-fmt/178	image/x-portable-pixmap, image/x-portable-anymap
PPM, binary	P6	fmt/408

Multi-image files

Although the Netpbm formats are usually thought of as single-image formats, the binary formats technically do support multiple images per file. This is accomplished simply by concatenating single-image files together. Such multi-image files are probably not well-supported.

See also

• ImgStar
• Netpbm
• PAM (Portable Arbitrary Map)
• PFM (Portable Float Map)
• PFS (Portable Floatmap Stream)
• XV thumbnail

Specifications

• PBM Format Specification
• PGM Format Specification
• PPM Format Specification

Software

The PBM/PGM/PPM/PNM formats are widely supported. Software listed here has been arbitrarily selected.

• Netpbm
• ImageMagick

Sample files

• http://www.fileformat.info/format/pbm/sample/index.htm
• http://samples.libav.org/image-samples/ → *.ppm, *.pgm
• http://www.csbruce.com/cbm/ftp/images/pbm/

Links

• Wikipedia: Netpbm format
• PBM, PGM, PNM, and PPM File Format Summary, from the Encyclopedia of Graphics File Formats
• Graphic describing PGM format
• Graphic describing PPM format