capture

What parameter can I use on a capture tag, to set the fromfile value to true.

I cannot find it anywhere. This is what I've tried, but it is not a valid parameter:

{{esl:signer1:capture:size(200,50),fromfile(true)}}

Or is there a way that I can modify all capture fields in a new package using the .NET SDK with text extraction, to use the SetFromFile(true) method, without knowing the names of the capture fields in the document?

Thanks in advance.