Re: [ft-devel] [Patch] Compensate blue zone rounding after scale

[Алексей Подтележников]

Why do you even create and calculate temporary shoot_delta?
You can explicitly increment/decrement blue->shoot.fit the same way
you do blue->ref.fit.
Like this:

+        AF_CJKBlue  blue;
+
+        if ( delta_t >= delta_b )
+        {
+          blue = &axis->blues[AF_CJK_BLUE_TOP];
+          blue->ref.fit += 64;
+          blue->shoot.fit += 64;
+        }
+        else
+        {
+          blue = &axis->blues[AF_CJK_BLUE_BOTTOM];
+          blue->ref.fit -= 64;
+          blue->shoot -= 64;
+        }


On Fri, May 13, 2011 at 7:37 AM, Just Fill Bugs <address@hidden> wrote:
> In af_cjk_metrics_scale_dim(), when we scale the blue zone to the font size,
> the blue zone is also rounded to pixel grid. The offset introduced in the
> rounding at both the bottom and top could have undesirable effect on the
> glyph height at certain font size.
>
> There are 4 states for the sum of top and bottom fit offset:
>
> 1. top + bottom >= 1.5 px    Round to 2 px
>
> 2. top + bottom >= 1.0 px    Round to 1 px
>       Bad Case: 0.5 + 0.5 => 1 + 1 = 2px > 1px
>
> 3. top + bottom >= 0.5 px    Round to 1 px
>       Bad Case: 0.4 + 0.4 => 0 + 0 = 0px < 1px
>
> 4. top + bottom < 0.5  px    Round to 0 px
>
> For the 2 bad results:
>
> 1st bad is OK, since we are OK with a pixel increase in size at small
> font size.
>
> 2nd bad is not OK. It shrink our already limited space by 1px at small
> font size. So we should compensate 1px in that situation.
>
> The patch only tried to fix the ref blue zone.
>
> The compensation kicked in at 11.5pt and 10pt and add 1px to the glyph
> height for wqy-zenhei.ttc.
>
>
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>



-- 
Alexei A. Podtelezhnikov, PhD