.PGM File Extension

Portable Gray Map Image

Developer Jef Poskanzer
3.6  |  46 Votes
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What is a PGM file?

A PGM file is a grayscale image file saved in the portable gray map (PGM) format and encoded with one or two bytes (8 or 16 bits) per pixel. It contains header information and a grid of numbers representing different shades of gray, from black (0) to white (up to 65,536). PGM files are typically stored in ASCII text format but also have a binary representation.

More Information

Screenshot of a .pgm file in Apple Preview 11
PGM file open in Apple Preview 11

PGM files include a header that defines the PGM format type ("P2" for text or "P5" for binary), image width and height, and the maximum number of shades. While binary PGM files may contain multiple images, ASCII PGM files may only include one image.

The PGM format is one of several image formats defined by the Netpbm project, which is an open-source package of graphics programs. Other formats include the portable bitmap (.PBM) and portable pixmap (.PPM) formats.

NOTE: PGM files may also be called "portable greymap" files.

How to open a PGM file

You can open a PGM file with various image viewers and editors. Some applications that support PGM images include GIMP (multiplatform), Corel PaintShop Pro (Windows), and Apple Preview (bundled with macOS).

Opening a PGM file with a text editor

PGM file open in Apple TextEdit
PGM file open in Apple TextEdit

Since PGM files are saved in plain text, you can also open them with a text editor, such as Microsoft Notepad or Apple TextEdit, or a source code editor. You may need to rename the .pgm file extension to .txt for the text editor to recognize it.

When opened in a text editor or source code editor, you can modify the image data in a PGM file. However, if you incorrectly edit the file, you may inadvertently corrupt the image.

How to convert a PGM file

Several image editors, including GIMP, Corel PaintShop Pro, and Apple Preview, can convert PGM files to other formats.

For example, GIMP can convert PGM files to many file types, including the following formats:

  • .JPG - JPEG Image
  • .PNG - Portable Network Graphic
  • .BMP - Bitmap Image
  • .TGA - Targa Graphic
  • .GIF - Graphical Interchange Format
  • .PS - PostScript File
  • .TIFF - Tagged Image File Format
  • .WEBP - WebP Image
  • .EXR - OpenEXR Image
  • .XCF - GIMP Image

Programs that open PGM files

Akai MPC Program File

Developer Akai
1.3  |  3 Votes

A PGM file contains a program used by various Music Production Controller (MPC) devices, such as MPC1000, MPC2000, and MPC3000. It stores configuration information about the pads (buttons) on the MPC device and the mono or stereo samples they are assigned to play when touched on the MPC device. PGM files also include parameters for the program, such as sound assignments, SIMULT settings, and tuning parameters.

More Information

PGM files may be saved in the standard MPC program format or the revised format that was developed to support more complex MPC devices. MPCs manufactured before the MPC1000 device do not support the newer PGM format. However, MPCs manufactured after the MPC1000 support both versions of the PGM format.

While PGM files were designed to be loaded on to MPC devices, they can also be loaded by MPC software developed to emulate MPC devices on computers. Some examples of programs that can open PGM files are MPC Maid and MPC Editor.

Programs that open or reference PGM files

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