• ImageMagick converts between a vast multitude of graphics file formats
  by: John Cristy
• ORTEP-III
  by: Michael N. Burnett and Carroll K. Johnson
• NCSA Scientific Visualization Software Suite
• GNU plotutils "includes several command-line applications for splining data and XY plotting. It also includes GNU libplot, a powerful library for device-independent 2-D vector graphics. Supported output formats include X11, Postscript, PCL5, Adobe Illustrator, and xfig."
  by: Robert Maier