.PGM File Extension
Portable Gray Map Image
| Developer | Jef Poskanzer |
| Popularity |
3.6 | 47 Votes |
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
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
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: