PAdES visual appearance: allow null as text color, preventing graphic operators
Created by: lion7
Currently a non-stroking color is always set when drawing a visual appearance on a PDF.
This can break PDF/A compliance if the document does not have an OutputIntent.
It would be nice if we could set text color to null
, so no graphic operators are used.
This is similiar to how the background color is implemented when it is null
.