ImagingDrawWideLine() in Draw.c has a bug in every version I've seen, which leads to different width lines depending on the order of the points in the line. This is especially bad at some angles where a 'width=2' line can completely disappear.
This is due to use of a cast vs. a floor in draw.c. Here is the fix:
<pre>
bash-3.2$ diff Imaging-1.1.6.orig/libImaging/Draw.c Imaging-1.1.6/libImaging/Draw.c
689,690c689,690
< dx = (int) (d * (y1-y0) + 0.5);
< dy = (int) (d * (x1-x0) + 0.5);
---
dx = (int) floor(d * (y1-y0) + 0.5);
dy = (int) floor(d * (x1-x0) + 0.5);
</pre>
Here is test program:
<pre>
import Image, ImageDraw
im = Image.new("L",(120,120))
dr = ImageDraw.Draw(im)
- vertical line going down
dr.line((5,5,5,45),width=2,fill=255)
- vertical line going up
dr.line((10,45,10,5),width=2,fill=255)
- horizontal right
dr.line((20,5,50,5),width=2,fill=128)
- horizontal left
dr.line((50,15,20,15),width=2,fill = 128)
- diagonal - slash
dr.line((10,70,30,50),width=2,fill=192)
dr.line((40,50,20,70),width=2,fill=192)
- diagonal - backslash
dr.line((70,10,90,30),width=4,fill=96)
dr.line((100,30,80,10),width=4,fill=96)
dr.line((50,30,65,35,80,45,90,60,100,75,100,85,95,90,90,90,
80,85,60,80,55,70,50,50),width=2,fill=255)
im.save('lines.png')
</pre>
Here is the image without the fix:
