Convert PNG to DLL

It doesn't seem to make much sense attempting to convert Portable Network Graphics directly to Dynamic Link Libraries (.png to .dll conversion), and it is, most likely, not even possible due to the nature of both file types. 

You might, however, be attempting to use your PNG graphics for icons stored in specific dynamic libraries. To do so, you need to search for special icon makers, especially tools, which actually let you export in DLL format. Unfortunately, most of those icon makers can import DLL files without probless, yet rarely export in DLL. Usually ICO is the preferred options.

It is also possible to generate new DLL files using tools, such as Microsoft Visual Studio, which, of course, requires knowledge of that software.