why my font size is always smaller than the given size

[mingfa]

Dear Everyone,

 

I am trying using freetype on Win32,

and I got one funny thing, that is, the font size displayed

is always a bit smaller than the given size. For instance,

 

 TT_Set_Instance_Resolutions(instance,120,120);    // 120 is my LOGPIXELSY
//    TT_Set_Instance_PointSize( instance, 100*72/120);
 TT_F26Dot6   pointSize;
 TT_Set_Instance_PixelSizes(instance,100,100,pointSize);

 

the given size is 100 pixels, but the size displayed on my machine

is only about 67 pixels!

 

Does anyboay know why?

 

Regards,

 

Mike