Round scale to nearest 26.6 fixed point.

With this change, the computation of the scale factor becomes
identical across the freetype and truetype packages, removing
deviations in the font metrics that are derived from scale.

The rounding computation is newer; it was introduced when the
truetype.Face type was added in commit 6deea24.

Fixes #85.

CONTRIBUTORS

@@ -27,6 +27,7 @@
 # Please keep the list sorted.
 
 Andrew Gerrand <[email protected]>
+Dmitri Shuralyov <[email protected]>
 Jeff R. Allen <[email protected]> <[email protected]>
 Maksim Kochkin <[email protected]>
 Michael Fogleman <[email protected]>

freetype.go

@@ -260,7 +260,7 @@ func (c *Context) DrawString(s string, p fixed.Point26_6) (fixed.Point26_6, erro
 // recalc recalculates scale and bounds values from the font size, screen
 // resolution and font metrics, and invalidates the glyph cache.
 func (c *Context) recalc() {
-	c.scale = fixed.Int26_6(c.fontSize * c.dpi * (64.0 / 72.0))
+	c.scale = fixed.Int26_6(0.5 + (c.fontSize * c.dpi * 64 / 72))
 	if c.f == nil {
 		c.r.SetBounds(0, 0)
 	} else {