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).
“myimage:param1=value1;param2=value2” will be passed to the loader as “resource” parameter.