.. _image-fitting:

Image fitting
-----------------

Users can fit multiple 2D Gaussian components to the selected file with the image fitting widget. Frontend sends :carta:ref:`FITTING_REQUEST` with ``file_id``, ``region_id``, ``initial_values``, and other settings. Backend fits the current channel and polarization of the file. For each fitting iteration, backend sends back :carta:ref:`FITTING_PROGRESS` to update the progress. When the fitting is complete, backend responds with :carta:ref:`FITTING_RESPONSE`. When there are newly generated modal and residual images, the new file IDs are incremented from the last opened image. 

Users can cancel the requested fitting with the progress widget. Frontend sends :carta:ref:`STOP_FITTING`, and backend sents back :carta:ref:`FITTING_RESPONSE` after the fitting is canceled.

The sequence diagram is shown below:

.. uml::
    
    skinparam style strictuml
    hide footbox
    title Image Fitting
    
    actor User
    box "Client-side"
    participant Frontend
    end box
    
    box "Server-side" #lightblue
    participant Backend
    end box

    User -> Frontend : Set fitting parameters
    activate Frontend
    Frontend -> Backend : FITTING_REQUEST
    activate Backend
    Backend -> Backend : Setup 2D Gaussian fitting
    loop
        Backend -> Backend : One fitting iteration
        Frontend <-- Backend : FITTING_PROGRESS
    end
    User -> Frontend : (Cancels the requested fitting)
    Frontend -> Backend : (STOP_FITTING)
    Frontend <-- Backend : FITTING_RESPONSE
    deactivate Backend
    User <-- Frontend : Displays fitting results
    deactivate Frontend