The function `_array_to_b64str` defined in the `_imshow.py` module (https://github.com/plotly/plotly.py/blob/master/packages/python/plotly/plotly/express/_imshow.py#L27) is quite useful in Dash apps with image processing. We could make it part of the public API (where ? probably in `plotly.utils` ?). What do you think @nicolaskruchten ? This was brought up recently in Almar's work (https://github.com/plotly/dash-3d-viewer/pull/2).