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| Name | PGM | JPG |
| Full name | PGM, Portable Gray Map Image | JPG - Joint Photographic Experts Group |
| File extension | .pgm | .jpg, .jpeg, .jpe |
| MIME type | image/x-portable-graymap | image/jpeg |
| Developed by | Jef Poskanzer | Joint Photographic Experts Group |
| Type of format | Raster image | lossy image format |
| Description | PGM files are known as portable graymap files and contain grayscale image information. These files can be saved in two representations, either as plain (ASCII) text or binary. In which way the PGM is saved is apparent in the file header. If the header contains the string "P2" it is a text format, if it contains the string "P5", it's a binary representation. Binary PGM files can contain more than one image. This is not possible for the text-based PGM. It is limited to one image. | JPG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPG typically achieves 10:1 compression with little perceptible loss in image quality. |
| Technical details | Portaple Gray Map Images can be encoded using either one byte or two bytes per pixel, representing either 8 or 16 bits. The file header contains different information such as the width and height of the image and the maximum number of black and white shades. The information is stored in a grit format, consisting of different numbers. These numbers represent the grayscale shades of the image, ranging from black (0) to white (65.536). | Image files that employ JPG compression are commonly called "JPG files", and are stored in variants of the JIF image format. Most image capture devices (such as digital cameras) that output JPG are actually creating files in the Exif format, the format that the camera industry has standardized on for metadata interchange. |
| Associated programs | ACD Systems ACDSee 18, ACD System Canvas 15, Adobe Photoshop with plug-in, Corel PaintShop Pro X8, GIMP, Inkscape, Netpbm | Apple Safari, Google Chrome, Mozilla Firefox, Internet Explorer, Adobe Photoshop, Paint Shop Pro, the GIMP, ImageMagick, IrfanView, Pixel image editor, Paint.NET, Xara Photo & Graphic Designer. |
| Wiki | https://en.wikipedia.org/wiki/Netpbm_format | https://en.wikipedia.org/wiki/JPEG |