COLOR24函数:将将8位RGB值转为24为颜色索引值

;+ ; NAME: ; COLOR24 ; ; PURPOSE: ; The purpose of this function is to convert a RGB color triple ; into the equivalent 24-big long integer. ; ; CATEGORY: ; Graphics, Color Specification. ; ; CALLING SEQUENCE: ; color = COLOR24(rgb_triple) ; ; INPUTS: ; RGB_TRIPLE: A three-element column or row array representing ; a color triple. The values of the elements must be between ; 0 and 255. ; ; KEYWORD PARAMETERS: ; None. ; ; COMMON BLOCKS: ; None. ; ; SIDE EFFECTS: ; None. ; ; RESTRICTIONS: ; None. ; ; EXAMPLE: ; To convert the color triple for the color YELLOW, ; (255, 255, 0), to the hexadecimal value '00FFFF'x ; or the decimal number 65535, type: ; ; color = COLOR24([255, 255, 0]) ; ; This routine was written to be used with routines like ; COLORS or GETCOLOR ; ; MODIFICATION HISTORY: ; Written by: David Fanning, 3 February 96. ;- FUNCTION COLOR24, number ; This FUNCTION accepts a [red, green, blue] triple that ; describes a particular color and returns a 24-bit long ; integer that is equivalent to that color. The color is ; described in terms of a hexidecimal number (e.g., FF206A) ; where the left two digits represent the blue color, the ; middle two digits represent the green color, and the right ; two digits represent the red color. ; ; The triple can be either a row or column vector of 3 elements. ON_ERROR, 1 IF N_ELEMENTS(number) NE 3 THEN $ MESSAGE, 'Augument must be a three-element vector.' IF MAX(number) GT 255 OR MIN(number) LT 0 THEN $ MESSAGE, 'Argument values must be in range of 0-255' base16 = [[1L, 16L], [256L, 4096L], [65536L, 1048576L]] num24bit = 0L FOR j=0,2 DO num24bit = num24bit + ((number(j) MOD 16) * base16(0,j)) + $ (Fix(number(j)/16) * base16(1,j)) RETURN, num24bit END ; ****************************** of COLOR24 **************************