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| | IDL Colors on a 24-Bit Display |
 | | The red index is taken to be the lowest 8 bits, the green index the middle 8 bits, and the blue index is the highest 8 bits of the 24-bit value. |
 | | Now, since most of us are not fluent manipulating the bits of a 24-bit number, the number is sometimes expressed in hexadecimal notation, where two digits are enough to set 8 bits at a time (i.e., 256 or 2^8 possible values can be set by two hexadecimal digets). |
 | | What this means is that IDL in this mode assumes that the value is a 24-bit value, and "decomposes" that value into three 8-bit values, which it uses to independently index the red, green, and blue locations in the color table. |
| www.dfanning.com /color_tips/colors24.html |
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