Using PyJAMAS as a context manager

When developing PyJAMAS plugins, or when using the PyJAMAS API in your code, it can be convenient to use/create a PyJAMAS instance that iterates over multiple images and/or annotation files. In that case, PyJAMAS can be used as a context manager in a with block. This means that, when the with block ends, the state of the PyJAMAS instance (including the open image, annotations, classifier, etc.) will be restored to what it was before the with block.

This code block illustrates how to use PyJAMAS as a context manager that loops over a list of images, applies a Gaussian filter, and saves the resulting image.

from pyjamas.rplugins.base import PJSPluginABC
from pyjamas.pjscore import PyJAMAS

apjs = PyJAMAS()
old_image = apjs.slices.copy()

# here we assume that a list of paths exists in list_of_image_paths.
with apjs:
    for an_image_path in list_of_image_paths:
       apjs.io.cbLoadTimeSeries(an_image_path)  # load the image.
       apjs.image.cbGaussianImage(sigma=2.0)  # apply Gaussian filter.
       apjs.io.cbSaveTimeSeries(an_image_path + "_gaussian")  # save the image.

# here, apjs will be restored to its state prior to the with block, and thus, this assertion should be True.
assert apjs.slices == old_image