Digital Image File Types Explained
Resolution Independence: Vector Images
The Vector format allows you to increase an image to any size without pixilation, due to its unique core structure. Vector files are usually saved as an EPS, or in their proprietary format, such as .AI (Illustrator).
Most image formats like JPEG and GIF are represented as pixels. Each pixel in the image stores digital numbers representing brightness and color. As you increase the size of the image, your software has to create new pixels and it estimates the color values of the new pixels based on the surrounding pixels…thus the image becomes “pixilated.”
Vector image formats contain a geometric description which can be rendered smoothly at ANY desired display size, as well as retain transparency. Vector images are usually created in applications like Adobe Illustrator or Macromedia Freehand. To convert a pixel-based image to a vector-based image, one might trace the image with a Pen tool in a program like Illustrator, or perhaps convert it in a program like Adobe Flash or Vector Magic and refine the results. This can be a tedious and time consuming process, depending on the details of your image.
Compression and Encoding: The Formats
JPG, GIF, TIFF, PNG, BMP. How do you choose? These and many other file types are used to encode digital images. The choices are simpler than you might think.
Part of the reason for the plethora of file types is the need for compression. Image files can be quite large, and larger file types mean more disk usage and slower downloads. Compression is a term used to describe ways of cutting the size of the file. Compression schemes can by lossy or lossless.
Another reason for the many file types is that images differ in the number of colors they contain. If an image has few colors, a file type can be designed to exploit this as a way of reducing file size. →
