[Image-SIG] fix for wide line directional dependence

[Randolph Bentson]

I've found that wide lines drawn with PIL 1.1.6 have a directional
dependence, e.g., lines from (0,0) to (-100,0) are thinner than those
from (0,0) to (0,-100).  The following patch seems to help, although
the lines still have a modest variation when rotating through the compass.

--- Draw.c_2745	2009-09-30 07:40:23.000000000 -0700
+++ Draw.c	2009-09-30 07:36:56.000000000 -0700
@@ -686,8 +686,8 @@
 
     d = width / sqrt(dx*dx + dy*dy) / 2.0;
 
-    dx = (int) (d * (y1-y0) + 0.5);
-    dy = (int) (d * (x1-x0) + 0.5);
+    dx = (int) (d * abs(y1-y0) + 0.5);
+    dy = (int) (d * abs(x1-x0) + 0.5);
 
     add_edge(e+0, x0 - dx,  y0 + dy, x1 - dx,  y1 + dy);
     add_edge(e+1, x1 - dx,  y1 + dy, x1 + dx,  y1 - dy);

-- 
Randolph Bentson
bentson at holmsjoen.com