It is not exactly what we need. We will access plantuml.jar very randomly. It can be single expression or multiple formulas at once. But we need a single call of plantuml.jar per expression. The "-clipboard" option must indicate a start of special mode for plantuml.jar. It looks in clipboard for text and ALWAYS generates a bitmap. That means, if an erroneuos state (no text, bad syntax, etc) will be occur, then a bitmap "Bad Input data" or similar schould be placed in clipboard. In our software it will be immediately visualized. As example i provide a some fragment of our symbolic processor
http://picsee.net/upload/2018-06-01/c90fc8abe9ce.jpg
The expressions will be first translated in AsciiMath text with colors and font states and then over call to plantuml.jar rendered in bitmaps. So we doing a loop over expresssions and will use in this loop plantuml.jar for current expression on the fly :-)
PS. Usage of FTP is limited for our clients due to their offline state or many restrictions to access an online service.