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Re: [ft-devel] regarding freetype 2 cubic curve flattening
From: |
Vivek Rathod |
Subject: |
Re: [ft-devel] regarding freetype 2 cubic curve flattening |
Date: |
Mon, 31 Oct 2011 17:13:10 +0530 |
On Mon, Oct 31, 2011 at 4:45 PM, Alexei Podtelezhnikov
<address@hidden> wrote:
> On Mon, Oct 31, 2011 at 3:22 AM, Vivek Rathod <address@hidden> wrote:
>> s is calculated as
>> "s = FT_ABS( dy * dx1 - dx * dy1 );" which means s is the perpendicular
>> distance of the control point from chord multiplied by L
>>
>
>> which means currently s_limit is being compared with perpendicular distance
>> of control point * L .
>
> Correct. s_limit is also multiplied by L on line 1065 in ftgrays.c:
>
> s_limit = L * (TPos)( ONE_PIXEL / 6 );
>
> I do not see a problem here.
The formula for deviation ( from Hein's paper).
d = dnorm * s ; here s is normalized ------------------- (1)
so the formula when s is not normalized becomes d = dnorm * (s / L) ;
-----------------(2)
and I think the L you are mentioning comes from this formula.
therefore s = (dmax/dnorm) * L;
Please correct me if I am wrong about this whole normalization assumption.
>
>> but s_limit is actual distance, so in order to do the correct comparison
>> (and to avoid division) don't you think we need to multiply s_limit once
>> more by L ?
>
> This is wrong. Look at the actual code.
>