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Page name: CGT - Compression [Logged in view] [RSS]
2006-11-11 21:32:24
Last author: wulfman
Owner: wulfman
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CG TOOLS



<img:img/drawing/19683_1095874738.jpg>  CGT - HARDWARE






<img:img/drawing/19683_1095874738.jpg>  CGT - GRAPHICS FILES



  <img:stuff/annee_greendot_house.jpg> CGT - File Attributes


   <img:img/drawing/80746_1099420452.jpg> CGT - Compression



Image files can be quite wasteful of file space, but as an array of colored dots it wasn't long before someone realized that rather than a file being written as an array, it could be written as a list. Rather than defining each pixel by its numeric value, any multiple identical values could be listed by the number of occurances; "print 8 dots this color, then 12 this other color... and so on. This list fits in a much smaller space for most web graphics. Other space reducion schemes developed to improve the use of larger images for web graphics include Pallet Optimized images, in which the number of colors used in an image is limited to 256, but they can be any 256 colors from a 32 bit pallet. The custom pallet is defined at the beginning of the file and the image displays with much better transition between colors, but with a limited range. This could be considered a form of compression, because colors that are not used, are not included in the CGT - Color Depth of the file, thus greatly reducing the size of the file.

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