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24 bit colour |
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24 bit colour is one of the ways used to represent RGB colour in an electronic format. Each repective value for red, green and blue in a pixel in an RGB image is represented by a byte (or 8 bits) of data - ie. each pixel in an RGB image needs 3 bytes (or 24 bits!). A byte represents a value in the range 0 to 255, which means that each of the red, green and blue components of a pixel in a 24 bit image can be one of 256 levels. Multiplied out, the total number of colours possible, using this format, exceeds 16.7 million. This is why 24 bit colour is sometimes referred to as millions of colours. The wide range of colours possible sometimes lead people to calling this true colour. If you think of the RGB cube (pictured to the right), we have simply marked 256 evenly spaced points along each edge (including the end points), and then used these to create a cubic lattice. Each intersection corresponds to a colour. You can see, that by varying the number of points we use to subdivide the cube, we can change the total number of possible colours. Another common format is thousands of colours, where each pixel in an image needs only 2 bytes of data. Some scanners and image editing applications can deal with 36 and 48 bit representations of colour.
Bytes and bits are units of memory -they represent a certain amount of space on a hard drive or in RAM on a computer. The amount of memory,
in bytes, that a 24 bit image occupies in its raw state, can
be found by multiply the number of pixels in the image by
3. Various file formats can be used to save 24 bit image data. Common formats include TIFF and JPEG (see http://www.soapplab.auckland.ac.nz/info/formats/). Both of these have the ability to compress image data so that it occupies less space when stored on a disk. |
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contact: web@creative.auckland.ac.nz |
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