Exploring implementation using Matplotlib as backend

[kakirastern]

I am interested in exploring the development of a non-interactive version using Matplotlib as the backend, towards a non-interactive version which would implement as much of the API as possible in a non-interactive format. However, I have never done anything similar. Is there any suggestions as to some workflow or just simple guidelines I should follow?

[pllim]

Thank you for your interest!

I can't say if mine is the suggested workflow, but personally, I would start with example_notebook/ginga_widget.ipynb. For prototyping, it would be easier to implement your version of astrowidgets.core.ImageWidget in your notebook cell. That way, you don't need to restart kernel or whatever to install your dev version constantly.

So, in your prototype, instead of from astrowidgets import ImageWidget, you would be using a local version of the ImageWidget. The goal is to replicate that notebook using your own implementation without changing the public API.

Public methods that are not working yet can raise NotImplementedError for now but they cannot be deleted.

However, optional keyword does not need to exist in your implementation but invoking them also cannot cause error. So a call like ImageWidget(logger=logger) -- while you do not have to necessarily do anything useful with the logger at this point, you have to support that API, so a **kwargs in your constructor would solve that problem right away.

@mwcraig or @eteq , feel free to correct me if I am steering @kakirastern in the wrong direction.

[kakirastern]

Thanks @pllim for the info!

[mwcraig]

This seems like a good way to go. It wouldn't be a bad approach to continue to use ginga to generate the underlying image but then display the image with matplotlib....though I suppose that the classes/functions in astropy.visualization helps quite a bit with converting a raw astronomical image to something displayable by matplotlib.

There is a pretty limited implementation of a simple image viewer using matplotlib at https://github.com/mwcraig/ccd-reduction-and-photometry-guide/blob/master/notebooks/convenience_functions.py#L6

https://github.com/mwcraig/ccd-reduction-and-photometry-guide/blob/master/notebooks/convenience_functions.py#L6 motivation for wanting a non-interactive backend like matplotlib is that the API written for the image widget is really convenient for setting up static plots too!

[pllim]

At one point, outside of notebook, I wrote a script to grab mouse click X & Y locations out of matplotlib imshow. But AFAIK, there is no way to natively have matplotlib then convert X & Y to RA & DEC, so that is something you need to re-implement using astropy.wcs.

https://github.com/pllim/playpen/blob/master/plot_click_example.py (no guarantee that it still works)

[kakirastern]

Thanks for the leads, I will definitely follow up on those

[kakirastern]

I really like the idea of using Ginga to render directly into a Matplotlib figure, even though support is limited to viewing widget itself. The strength would definitely be in the overplot options.

[kakirastern]

BTW, I might as well just call my version of the widget MatImageWidget...

[mwcraig]

Maybe MattImageWIdget? 😉

[pllim]

Matplotlib is usually shortened to MPL.

[pllim]

I don't know what is the benefit of using this widget if it requires Ginga anyway. Ginga also can overplot by overlaying its canvas objects. IMHO I would use this if I want publication quality plots without having to install Ginga. Matt, what is the use case that you have in your mind for this implementation?

[kakirastern]

Ah, I see... then I will go without Ginga then, just Matplotlib.

[michiboo]

I have try to just use Matplotlib but notice the quality of the image was not as good.

[kakirastern]

Hi @michiboo, would it be possible to share a bit of the details about your Matplotlib settings for the displaying of the images? Would like to see if I will get the same qualify with my setup or if I can reproduce the "qualify problem".

[kakirastern]

Matplotlib can produce quite good resolution images from my experience...