problem with attachement_fu on sinatra

Hello experts,

I am trying to user attachement_fu plugin on sinatra..

When I'm posting request on sinatra.. including file params

then in log it showing posted params[:file] format in hash type.. like

{"uploaded_data"=>
  {:filename=>"user.JPG",
   :type=>"image/jpeg",
   :name=>"custom_thumbnail[uploaded_data]",
   :tempfile=>
    #<File:C:/DOCUME~1/Nishant/LOCALS~1/Temp/RackMultipart4072-15639>,
   :head=>
    "Content-Disposition: form-data;
name=\"custom_thumbnail[uploaded_data]\";
filename=\"user.JPG\"\r\nContent-Type: image/jpeg\r\n"}}

instead of as attachement_fu needs it request file params as like

{"uploaded_data"=>
  #<ActionDispatch::Http::UploadedFile:0x1434
   @content_type="image/jpeg",
   @headers=
    "Content-Disposition: form-data;
name=\"custom_thumbnail[uploaded_data]\";
filename=\"user.JPG\"\r\nContent-Type: image/jpeg\r\n",
   @original_filename="user.JPG",
   @tempfile=
    #<File:C:/DOCUME~1/Nishant/LOCALS~1/Temp/RackMultipart4072-15640>>}

Due to above(first one) has type format attachement_fu is not
supporting..

it showing errors like

undefined method 'content_type' and all other....

Any ideas..? on how to get this to change/access params format as normal
format(like action_controller params)?

Thank you in advance

-Ganesh K