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Computer Image File Formats

If you have ever worked with computer graphic images, whether they be from digital cameras, found on the web, or you create them yourself, then you know there are a lot of image file formats that are available. This is because each format stores the image in a certain way that makes it the best choice for a given situation. This tutorial will cover the most common image formats that you will find on the Internet or with your devices, such as a digital camera, and how they are used. Before we go into the discussions on the actual image formats it is important to discuss the various attributes that image file formats can have.

The Attributes and Terms

Compression

Compression is the act of reducing the file sizes of images. When images are stored in their raw format, without compression, their file sizes can be very large. This causes the images to take up a lot of storage space and, furthermore, take a long time to transfer over the Internet.. Compression techniques alleviate these problems by reducing the file sizes to a much more manageable size that can easily be stored and transmitted over various mediums. Almost all image formats use different forms of compression, so as an example, we will only discuss the compression technique GIF files use so that you can see how an image is compressed into a smaller file size.

GIF compression works by finding repetitive patterns in particular colors and instead of listing each pixel and its color, lists instead the amount of repetitions there are for a particular color. For example if a GIF image has 60 pixels of the same color in consecutive order, instead of adding that pixel color 60 times in the image file, it will instead enter the amount of times the color is repeated. The below figure represeents an image file that has a height of 1 pixel, and a width of 14 pixels. The first 8 pixels are the color Red and the last 6 are the color blue. When the file is uncompressed the image file will represent each pixel as it is seen in the actual image. When it is compressed it instead puts an index of the amount of times a pixel color is repeated consecutively. In the figure below you see the uncompressed image shows 8 Red Pixed and 6 Blues pixels and each pixel is represented. In the compressed format you see the index 8 preceeding the R, for red, and the number 6 before the B, for blue. That tells the image that there are 8 consecutive red pixels and then 6 consecutive blue pixels.. As you can see the amount of storage space saved by this method can be significant..