-draw produces a pimple on circles and arcs

[rmabry]

The following command draws a circle. But the circle has a zit.

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convert -size 200x200 xc:white -fill black -draw "circle 100,100 180,100" PNG32:badcircle.png

Zoom in on the rightmost pixels and you'll see this:



A fix? In the file draw.c, in the function TraceEllipse() are the following lines, the fifth of which can be changed to get rid of the zit, by dropping the subtraction of MagickEpsilon.

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angle.x=DegreesToRadians(degrees.x); 
  y=degrees.y;
  while (y < degrees.x)
    y+=360.0;
  angle.y=(double) (DegreesToRadians(y)-MagickEpsilon);
  

The asymmetry between the x and y variables made it suspicious. But I don't know what else the change breaks, and I'm sure the subtraction is there for a good reason.

The following is an amusing workaround. The blue figures are made using an angle range of -180 to 180 instead of 0 to 360, and those figures seem unblemished.

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convert -size 400x400 xc:white -fill black -draw "circle 200,100 250,100 arc 50,250 150,150 0,360 ellipse 100,320 80,40 0,360" -fill blue -draw "arc 250 ,250 350,150 -180,1 80 ellipse 300,320 80,40 -180,180 " PNG32:badcircles.png

This is 6.8.0-5 2012-11-03 Q16 on Windows 7.

Rick

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.8.0-8 Beta available by sometime tomorrow. Thanks.