GIMP Image Editor: How to edit images into PGM ?
- GIMP: GNU Image Manipulation Program.
 - GIMP Image Editor is a Free and Open Source Image Editor. click here to download and install.
 - It is used for converting images into a PGM Extension.
 
        Different Type of Image Extension:  
             JPEG ->  Joint Photographic Experts Group
             PNG ->   Portable Network Graphics
            XCF ->   eXperimental Computing Facility
             PGM ->  Portable Gray Map
-> In image processing technique, we have to take input as an image. So, the most efficient extension for input image is the ".PGM" extension image.
-> The ".pgm" extensible Images are editable in a text editor.
-> The ".xcf, .png, .jpeg" extensible images are not editable in a text editor.
-> ASCII: American Standard Code for Information Interchange.  
Process of Converting Images into a PGM Image:
->  Download the GIMP File -> Install.
-> Download image  ->  Save Download Image  ->  "Right Click" on saving image  ->  go to "Open with" and  ->  click on "GIMP Image Editor"  ->  Go to the "file" in open image ->  Click on "save as..."  ->  Go to top and Change the Name: of the file extension into "pgm"  ->  Go to right bottom corner, click "Save"  ->  Click "Take me to the Export dialog"  ->  Go to Right bottom corner and click "Export"  ->  Choose "ASCII"  ->  Export.