Ability to style download image for chart

[AlexVvx]

Hi, what do you think about adding ability to style downloaded image differently, then original chart? E.g. margins, borders - update appearance of chart exported to image.

[etpinard]

See https://codepen.io/etpinard/pen/BwvENX?editors=0010

Since #1939 released in 1.30.0, Plotly.downloadImage and Plotly.toImage accept {"data":[], "layout":{}} objects as well as graph div as first argument.

So one could extend a graph's data and/or layout before calling Plotly.downloadImage to apply custom download styles to a graph. I don't see the need to add a style option to Plotly.toImage.

[AlexVvx]

Sounds good. A couple of questions:

• does it mean, that arguments list probably won't change and it's ok to use {data, layout, config} ?
• _snapshotInProgress probably won't work. It's possible to update it manually in your app code, but is it ok to use property with underscore, since it supposed to be used internally?

[etpinard]

does it mean, that arguments list probably won't change and it's ok to use {data, layout, config} ?

The api is the following, so yes, it isn't the same as newPlot.

_snapshotInProgress probably won't work

I don't know what that is. It's probably always a bad idea to rely on _ properties.

[AlexVvx]

_snapshotInProgress - from plotly.js/src/snapshot/download.js,
true - if snapshotting already in progress, will cancel next download process when first one is not finished
false - if not in progress

[etpinard]

It should.

Alright, I'm closing this thing as it won't result in a PR of any sort. Please use https://community.plot.ly/ if you have other questions of the likes.