Compression/Date compression is used on file formats to decrease the amount of data so more room is saved.
Compression in image files is used to reduce the size of the file, many image films are designed to compress information in any possible way as they can varie drastically in size. When a file is compressed it can save up to 50% less disc space than the original file.
Image compression is either lossy; information can be lost permantly to decrease file size, or lossless; some of the information can be returned.
Lossy
Lossy compression is a method used to compress data however some of the data will be lost as it reduces the number of colours within it, often reducing the quality. Nevertheless the file is reduced in size.
Lossless
Lossless compression is a method used to compress the data, however lossless compression unlike Lossy compression allows an estimation of the exact original to be reconstructed to its orignial state.
The image's of the Owl show the extreme difference compression can make. As you can see the (above) image is crisp and clear with defined lines and colours, as it contains more information. However the image (below) is pixelated, due to compression to make the file smaller so it has lost information in places.
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| 504kb Original before compression |
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| 34kb Image after compression |
The image's of the Owl show the extreme difference compression can make. As you can see the (above) image is crisp and clear with defined lines and colours, as it contains more information. However the image (below) is pixelated, due to compression to make the file smaller so it has lost information in places.
Image Capture
Ways of capturing digital images:- Digital Camera
- Scan / photocopy
- Phone Camera / uploading
- Drawing Tablet
- Capture card
- Tablet computer (ipad)
Optimisation
Optimisation allows an image to maintain the quality needed despite the size, it is used to allow aspects of games and websites to load high quality images with a small image data. This is done by following the 'power of two' rule.
Power of two rule
These rules are simple yet very afftective, they apply to all game associated images. This rule makes sure the image's conform to a series of regular dimensions. This usually means deviding down or doubling up by two, Making sure all the images in a game are in proportion to each other, resulting in quick loading smooth game.
The images (above)(right) is an example of what would happen if a texture was placed on a 3D shape without using the power of two rule. A/B are uneven with parts of the 3D shape still visible. This would look poor in a game and would make it take twice aslong to load.
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