[LIBART] Can anyone explain this problem?

[Peter Montgomery <pjmonty csi com>]

Hi,

    I compiled LibArt and the test program.  When I ran it, I got errors
in the images.  I decided to simplify the image being made and created a
simple square with a one pixel vertical skew.  This is the code to fill
the points...


  // These generate a square
 vec[i].code = ART_MOVETO;
 vec[i].x = 101;
 vec[i].y = 20;
 i++;

 vec[i].code = ART_LINETO;
 vec[i].x = 10;
 vec[i].y = 20;
 i++;

 vec[i].code = ART_LINETO;
 vec[i].x = 11;
 vec[i].y = 140;
 i++;

 vec[i].code = ART_LINETO;
 vec[i].x = 102;
 vec[i].y = 140;
 i++;


The image is attached below.  Can anyone shed any light on this?  I have
tried compiling this under both VC++ on Windows and GCC on Linux and get
the same results.

    Thanks,
    PeterM

PS - I saved the JPEG with the most minimal compression available, so it
should be basically artifact free.  If you zoom in on the image, you'll
see that the anti-aliasing is working fine, but some scanlines are
shifted an integer pixel over.

Attachment: SquareError.png
Description: PNG image