ras A .ras extension file is a binary raster image format file that was developed using the UNIX platform by Sun Microsystems. It uses the bitmap format that is simple to use and has the ability to store data in grayscale, black and white as well as colored pixels. The basic layout of a .ras file begins with a header, is followed by a color map and finally by the image data that is bitmapped.
sgi A .sgi extension file saves images in the original Silicon Graphics Image format. These files are originated from the library of SGI images that were there on every Silicon Graphics machine. SGI files are also referred to as RGB, IRIS or Irix RGB., .sgi image files can be saved in 8-bit color, 16-bit or 32-bit color. GIMP has the compatibility to read and write .sgi extension files and also has a dialog box that pops up to help select the compression type. The preferred compression is RLE and while it reduces the file size, it is advisable to check once it is done to ensure that the file size is indeed reduced as sometimes the size is more than the actual file size.