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1631Re: corrupted symbols: analysis and solution

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  • Andrew Schulman
    Oct 3, 2005
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      > - ploticus generates symbols using its standard line drawing and/or
      > polygon fill operations
      >
      > - the standard drawing operations basically have no information about
      > what "device" the graphic is being rendered on, eg. where GD pixels are.
      > Ploticus supports a number of output "devices", some raster and others
      > vector.

      Right.

      > - it's likely that antialiasing wouldn't be an ideal solution for
      > scatterplot symbols

      OK

      > - a possible solution that comes to mind would be to implement an
      > alternate way to render data point symbols that would work at the device
      > pixel level.. this would be available in addition to the current method.
      > This would avoid having to meddle with the current stable code and doesn't
      > seem like it would be too hard. Perhaps it would be available only w/ GD,
      > at least at first.

      I agree, this sounds like a promising approach and could start just w/ GD
      (which is all I care about at present :). Based on just my one perusal of the
      ploticus code, it seems that most of the work could be done by adding an
      alternate set of definitions of the E* macros? I'll have to think about
      that...

      > - also note that ploticus has always supported the use of small png images
      > as plot symbols.. see the description for "imgfile" here:
      > http://ploticus.sourceforge.net/doc/symboldetails.html ... These would be
      > immune from rounding effects but probably not ideal (I believe that there
      > are issues when data points are overlapping or close together & png
      > doesn't support transparency). I haven't tried this lately.

      Right, OK. Possibly useful, although a separate PNG would have to be created
      for each symbol.
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