TColor與RGB分量的關(guān)系及轉(zhuǎn)換函數(shù)（巧用$來把16進制轉(zhuǎn)10進制）

aaie_ 2012-08-08

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幫助文檔中對Tcolor的說明如下：

If you specify TColor as a specific 4-byte hexadecimal number instead of using the constants defined in the Graphics unit, the low three bytes represent RGB color intensities for blue, green, and red, respectively. The value $00FF0000 (Delphi) or 0x00FF0000 (C++) represents full-intensity, pure blue, $0000FF00 (Delphi) or 0x0000FF00 (C++) is pure green, and $000000FF (Delphi) or 0x000000FF (C++) is pure red. $00000000 (Delphi) or 0x00000000 (C++) is black and $00FFFFFF (Delphi) or 0x00FFFFFF (C++) is white.

TColor 值是以十六進制進行存儲的，低三位分別表示紅、綠、藍三色，就像例子中所說$000000FF紅，$0000FF00綠，$00FF0000藍。

知道其結(jié)構(gòu)組成后由Tcolor轉(zhuǎn)到RGB的分量就非常簡單了。

這里用到字符串處理函數(shù)，十六進制轉(zhuǎn)十進制函數(shù)等（這個轉(zhuǎn)化比較巧妙！）……

function 
getRGBText(AColor:TColor):string; 
var
sHexRGBResult:string;//$00FF8080為固定格式 
sR,sG,sB:string; 
begin
  FmtStr(sHexRGBResult, '%s%0.8x', [HexDisplayPrefix, 
Integer(AColor)]); 
 //使用StrToInt函數(shù)可以實現(xiàn)十六進制換十進制，具體代碼是：StrToInt('$' + 'FF'); 
 //這時值等于255。也就是在'FF'前加上一個'$' 
  sR:=IntToStr(StrToInt('$'+RightStr(sHexRGBResult,2))); 
  Delete(sHexRGBResult,8,2);//$00FF80變成這樣 
  sG:=IntToStr(StrToInt('$'+RightStr(sHexRGBResult,2))); 
  Delete(sHexRGBResult,6,2);//$00FF變成這樣 
  sB:=IntToStr(StrToInt('$'+RightStr(sHexRGBResult,2))); 
  Result:='RGB('+sR+','+sG+','+sB+')'; 
end;