[Image-SIG] Troubles with ellipses

[Joe Reinhardt]

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I am trying to draw an ellipse onto a PIL canvas.  I wasn't able to
find much documentation on the ImageDraw.ellipse method, but I think I
properly determined the order of arguments to specify the major and
minor axes.  My trouble is that one of the axes is coming out a bit
too short.

Attached below is an example.  I was expecting to see an ellipse
exactly inscribing the rectangle.  However, the bottom edge is off by
one pixel.

Any ideas?


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Content-Type: application/octet-stream
Content-Disposition: attachment; filename=el.py
Content-Description: Ellipse test code

#
# ellipse test
#

import Image, ImageDraw

size = 255
r1 = 40
r2 = 55
center = (size - 1)/2

im = Image.new("L", (size, size))
draw = ImageDraw.Draw(im)

print "center = " + `center`
print `[center - r1, center - r2, center + r1, center + r2]`
    
draw.rectangle([center - r1, center - r2,
                center + r1, center + r2], 255)
draw.ellipse([center - r1, center - r2,
              center + r1, center + r2], 150)    

im.show()

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-- 
Joseph M. Reinhardt                      joe-reinhardt@uiowa.edu
Department of Biomedical Engineering     1402 Seamans Center
University of Iowa                       Iowa City, IA 52242
Phone: 319-335-5634                      Fax: 319-335-5631

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