Digital Image File Compression

Image file compression algorithms come in two types, lossy and lossless:

* Lossless compression reduces the file size with no loss to the quality of the image, even though the compression ratios may be weak. If an image is to be printed or the quality is more important than the file size, lossless algorithms are preferred.

* Lossy compression takes advantage of the limitations of the human eye and discards information that can't be seen. These algorithms allow for variable levels of compression, and as they are compressed, the file size is reduced. The more the file is compressed, the more the image deteriorates and becomes noticeable; this is called artifacting.

The JPEG software incorporates an algorithm Exif (Exchangeable image file) format used in most cameras. This is used to standardize and record the exchange of data between editing and viewing software and the digital camera. Recorded for individual images, the data includes:

* Time and date

* Shutter speed

* Camera settings

* Exposure

* Image size

* Name of camera

* Color information

* Compression

Using image editors to view the pictures, this information can then be displayed.

PNG, JPEG and GIF are the most common file formats used on the Internet. There are two main families of graphics: raster and vector.

JPEG (Joint Photographic Experts Group) image files are of the lossy format. Most digital cameras have the ability to save to a JPEG format (the DOS extension for JPEG is JPG). This format supports 8-bit per color RGB (red, green, and blue) for a 24-bit total, and it creates relatively small files.

In most situations, the compression doesn't distract from the image quality. However, JPEG files do degrade more as they are repeatedly saved, so it is best to store images in a lossless non-JPEG format.