Joint Photographic Experts Group (Jpeg)

This is the standardized method of lossy compression, typically using a 10:1 compression rate with little perceivable quality degradation.

The most commonly used file format is JPEG/Exif, which is industry standard in most image capture software.

Advantages:

· There is universal support for this format, used or useable by every image capture device and image manipulation software.

· Small file size due to the average 10:1 compression ratio.

· No editing is required to print the image

Disadvantages:

· As it is a lossy format some quality will always be lost when the image is compressed.

· Settings from the camera that takes the photo are applied, meaning the user may have to later edit the image if the camera settings are not to the user’s preference.

Graphics Interchange Format (GIF)

GIF is the standard format for animated images, generally used for simple animations over true colour images as it is limited to 8 bits per pixel; this means that the format can only use a palette of up to 256 colours.

Advantages:

· Supports animations

· It uses lossless compression

· Suitable for images with relatively few colours

· Supports transparency

· Wide spread support – Most image editing programs and browsers support GIF

Disadvantages:

· Only 8 bits per pixel, limiting the image to a palette of 256 colours

· Animations only play in browsers that support the format, file system explorers rarely play them

· The image cannot be edited after being encoded as an animated GIF or the animation sequence will be lost

Tagged Image File Format (TIFF)

TIFF is commonly used by amateur and professional artists alike in the publishing industry to store images. The stored images can be lossy or lossless format, although they are almost exclusively used as lossless.

Advantages:

· Flexible, can represent everything from fax images to compressed or uncompressed photos as bitmaps.

· Support for all possible colour depths and multiple images.

· Used in digital cameras as a lossless format

· Operating systems have built in image viewers with support for TIFF

Disadvantages:

· As files are not compressed by default the file size is generally large

· Most files are too large to send via email

· Most web browsers cannot open TIFF files

Portable Network Graphic (PNG)

PNG is a form of bitmap image, using lossless compression, designed as a license free replacement for GIFs. The main purpose of this format is for the transfer of images online, not being suited for printed graphics.

Advantages:

· Open source - There are no patent restrictions

· High level of transparency support

· Small file sizes

· Lossless compression format

· Can be saved as 8bit/24bit/64bit

Disadvantages:

· Despite being designed to replace GIF, PNG does not support animation.

· Only supports RGB, therefore is unsuitable for printed images

Compression Techniques

Lossless

Lossless compression allows the original data to be exactly rebuilt from the compressed data. Certain formats, such as PNG and GIF only use lossless compression, making them ideal for the compression of images that must be perfectly replicated.

Lossy

Lossy Compression discards portions of the file’s data, resulting in varying degrees of quality degradation depending on the level of compression used. Significant quantities of data can usually be discarded before there is notable degradation. JPEG uses this format to achieve a lower file size with a barely noticeable quality loss.

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