是直接对彩色位图的像素作灰度转换，其中不需要涉及调色板。如果使用调色板，是 需要对系统调色板以外的其他调色板条目作灰度替换后，应用给位图就行。-Directly to the color pixel for grayscale bitmap conversion, which involves no palette. If you use the palette, the palette is required other than the system palette entries as