Chart::PNGgraph is a graph plotting module (deprecated).
Chart::PNGgraph is a perl5 module to create PNG output for a graph.
Chart::PNGgraph is nothing more than a wrapper around GD::Graph, and its use is deprecated. It only exists for backward compatibility. The documentation for all the functionality can be found in GD::Graph.
This module should work with all versions of GD, but it has only been tested with version 1.19 and above. Version 1.19 is the last version that produces GIF output, and requires a conversion step. The default distribution of Chart::PNGgraph uses Image::Magick for this. If you'd like to use something else, please replace the sub png2gif in Chart::PNGgraph::Convert with something more to your liking.
Note that if you use Chart::PNGgraph with a GD version 1.19 or lower that any included logos will have to be in the GIF format. The only time that PNG comes into play is _after_ GD has done its work, and the GIF gets converted to PNG. There are no plans to change that behaviour; it's too much work, and you should really be upgrading to a version of GD that produces PNG directly.