颜色取反 rgb COLORREF

 

编码时遇到下面问题

 

背景颜色和前景颜色需要取反

 

COLORREF m_clr[5];

 

//背景颜色

 m_listPD.SetItemData(nCount,m_clr[nUltraOrder]);
 //字的颜色取反
 m_listPD.SetItemColor(nCount,0xFFFFFF - m_clr[nUltraOrder]);  

 

方法即是

0xFFFFFF - $oldcolor

 

转自

http://zhidao.baidu.com/question/143793592.html?push=ql

 

echo dechex(0xFFFFFF - $oldcolor);

把原文贴出来吧，不然可能不知道怎么来的。

You can invert a color by subtracting each of its red, green, and blue components from 255. In other words:
    new_red   = 255 - old_red
    new_green = 255 - old_green
    new_blue  = 255 - old_blue
You can break a color into its components, use this technique to invert the components, and then use RGB to recombine them into the inverted color. However, there is a much simpler method.

If a color's components are given as R, G, and B, then the color is represented as:

    R + 256 * G + 256 * 256 * B
Now consider the representation of inverse of this color with components 255 - R, 255 - G, and 255 - B:

    (255 - R) + 256 * (255 - G) + 256 * 256 * (255 - B)
  = (255 + 256 * 255 + 256 * 256 * 255) -
    (R + 256 * G + 256 * 256 * B)
  = &HFFFFFF - the_original_color
So a simpler method for calculating the inverse of a color is:

    new_color = &HFFFFFF - old_color