Unit 30 - Task 8

File Format

File formats are the various ways in which files can be saved. The format that you choose to save your file as depends on its content, size and quality. For low quality windows media files, you would save them as.wmv. If you were saving a PowerPoint, you would save it as a ppt. file. There are many different file formats, but no matter what format you save it as, the higher quality the file is, the more space it will take up.

Compression Techniques

Data compression involves encoding information using fewer bits than the original representation; Compression can be either lossy or lossless.

Lossy compression reduces the file size by identifying unnecessary information and removing it. Although this produces the smaller file size, it can result in images becoming distorted. For example it could be reduce the colour space to the simplest colours in the image, resulting in 6 or 7 colours rather than 256.

Lossless compression reduces the file size by identifying and eliminating any wasted "space" used to transmit the data. It produces a larger file size, but overall the image quality a lot better. For example, an image may have areas of colour that do not change over several pixels; instead of coding "red pixel, red pixel, ..." the data may be encoded as "279 red pixels".

Image Resolution

Image resolution refers to the sharpness and clarity of an image. The higher the resolution the sharper, more defined, and more detailed the image will be. However, an increase in resolution also leads to an increase in file size. This may pose a problem if you are looking to display the image on a website, as the file size might be too big. A higher resolution is therefore better for image quality, but it also leads to an increase in file size.

Colour Depth

Colour depth refers to the levels of colour that are found in a graphics display. The greater the colour depth, the higher number of pixels used to show the colour of a bitmap image. A higher colour depth therefore leads to a better quality image with more intricate colour and the definition, but it also leads to an increase in file size, as there are more colours and details being expressed.