In the world of CAD (Computer Aided Design) there are many types of files used for images, drawings and models. Since understanding these file types and extensions is important we have created this glossary which lists many of the typical ones you will find when working with graphics and CAD programs.

Let us first examine two of the main types of computer generated images:

Vector Image: This type of image consists of geometric formulas that describe the shape or lines that it is composed of. This means that instead of being made up of pixels that may not provide as high quality resolution, it is composed of pure mathematical formulas. This means that as the image is modified to have a different size or orientation the formulas stay the same and the image keeps its core properties intact.

Raster image: A raster image is also known as a bitmap image. It consists of small dots called pixels that have specific colour values assigned to them. The resolution of this type of image is denoted as dots per inch (dpi) or pixels per inch (ppi). Therefore raster images are resolution dependent meaning that as the size increases or decreases the quality of the image is affected.

The following are some of the common file extensions used in CAD and other computer design programs:

AI: This file extension signifies that the file is an adobe illustrated file and that the drawing is in the form of a vector.

DXF: This is an open sourced CAD file format. This means that both 2D and 3D designs can move between AutoCAD and other programs. This file format is universally compatible with most CAD programs and is widely used in the industry.

EPS: EPS stands for Encapsulated PostScript. These files can contain both vector and bitmap images. Adobe Illustrator is one of the most common programs used to create EPS files while Photoshop possesses the ability to save bitmap files as EPS.

JPEG: JPEG stands for Joint Photographic Experts Group which created this image file format standard. The JFIF (JPEG File Interchange Format) is another form that JPEG images are often stored under and often referred to as JPEG as well. These are bitmap files which mean they are composed of pixels.

PNG: PNG stands for Portable Network Graphics that was created to replace the GIF (Graphics Interchange Format).  It is a file type that stores bitmap or raster data, and does not lose any image quality during compression. This type of file is not commonly used for print applications because it does not support CMYK colour spaces, but is used for many online images or graphics.

HPGL: HPGL stands for Hewlett-Packard Graphics Language. It is the printer instruction file used for plotter printers. Plotter printers use lines to print graphics rather than using dots as like many other types of printers. This file type usually contains setup commands and then the corresponding graphics commands.

DWG: This type of file is in a binary format that is used to store 2D and 3D design data and is very similar to the DXF file extension. It is a common form used in may CAD programs.

3DM: 3dm stands for 3D metafile and is an open source format allowing CAD/CAM software to work with 3D geometry and models.


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