Settings for export in png

The default settings are actually taken from the dimensions of the diagram itself. Every new diagram (if not created using a template) will be 13 cm wide and 10 cm high. This is also the size in which it will be displayed if the adjustment to the window size has been turned off. One can change the diagram dimension in its property dialog or by resizing it with the mouse. The new size will be the default export setting.

With FPScript, it is not possible to alter the state of (presentation) objects, this is subject to VBA via Automation.