A possible approach:

1. define your own “image URI format”. For example


The image URI format should include all params, you mentioned, required by the image generating script.

2. implement a custom resource loader, which “understands” and can process the introduced image URI format (parses the parameters, requests the script to generate an image and returns the image back).

See http://pd4ml.com/cookbook/custom_rc_loaders.htm
“myimage:param1=value1;param2=value2” will be passed to the loader as “resource” parameter.