Re: [ft] what's the mean of CEIL( x )?

[David Turner]

luoyi a écrit :
> sorry, maybe I misunderstand what is "fixed-point 26.6 number".....
> can you explain it ?
>
>   
it means that the value of X can be seen as a 26-bit integer, followed 
by a 6-bit
fractional part. As in the following graphics:

 +----------------------------------+-----------+
 |     integer mantissa             | fraction  |
 +----------------------------------+-----------+
             26 bits                    6 bits
                             

In other words:

 float_value(x) =    (x >> 6) + (x & 63)/64.0

 round(x) = (x+32) & ~63
 floor(x)   = x & ~63
 ceil(x)     = (x+63) & ~63
 int(x)       = (x >> 6)

the macro CEIL(x) as defined really returns int(ceil(x))

note that int(x) is (x >> 6) and *not*   x/64.0 !!

Hope this helps,

- David Turner
- The FreeType Project  (www.freetype.org)



                  


> "David Turner" <address@hidden> ??????:address@hidden
>   
> >   x=240 corresponds to value 3.75 CEIL(240) => 4
> >     
>
> 240 / 26.6 =  9.022
>
>
>
>
>
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>   


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