There are probably several ways how Microsoft Visio drawings might be exported as common PNG drawings. The easiest way is to do it with ZAMZAR online conversion service, that support great many file formats.
Convert Microsoft Visio diagram document to Portable Network Graphic.
We have found 4 software records in our database eligible for .vsd to .png file format conversion.
Microsoft Windows software - convert vsd to png on Windows
Visual processor used to create high quality presentations, charts and graphs
Convert from vsd file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned vsd to png. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert vsd to png on OS X
Mac version of popular presentation software from Microsoft
Multiplatform software - convert vsd to png on any platform
A vector graphics editor
Graphic and diagram software from LibreOffice suite