Pypnm

New version trying to reduce resource load.

For previewing with `list2bin` LA and RGBA images may be rendered against chessboard background (optional, controlled by new `show_chessboard: bool`. Default is `False` for backward compatibility.

Memory usage for writing files reduced. Memory usage for display remain unchanged since, first, you must have whole image to display loaded in memory anyway, second, you are assumed not to try displaing images of 10000x10000 pixels size.

1.13.10.7.pypi
PyPNG 1.13.10.7 version, module documentation harmonized with PyPI release.

Viewer update, GUI improved.