Snapshot routines should allow users to specify image width/height

[etpinard]

Motivated by #42 (comment)

At the moment, the Snapshot.toImage has hard-coded width and height parameters.

Something like:

Plotly.Snapshot.toImage(gd, {format: 'png', width: 1000, height: 800});

Moreover, maybe the on-success handler used by the modebar toImage button could be used as the default on-success handler to Snapshot.toImage

[sglyon]

Ping, any update on this?

[etpinard]

We're still doing experiments with potential APIs. No serious work has gone into this to date.

That said, once we figure out how to expose things to the users, this should be a 2-day project.

[etpinard]

Once we're comfortable with the API, we should expose the toImage on the Plotly directly.

Moreover, we'll need toImage to return a promise, like the other Plotly async methods.

[gramster]

Is there a way to get raw PNG data from a plot snapshot? We would like to do this so that we can generate a PNG output in an IPython notebook so that when viewing the .ipynb file in Github or elsewhere where Javascript is not executed there is a static fallback version that gets displayed.

(and we need to do this in the Javascript code, not Python)

[sglyon]

You should be able to do Plotly.Snapshot.toImage(gd, {"format": "png"}), which will return a promise you then have to deal with resolving.

[gramster]

Thanks. I don't see docs on Plotly promises. I tried this:

var idata;
Plotly.Snapshot.toImage(model.dom.id, {"format": "png"}).then(function(d) { idata=d; })

but I get:

Plotly.Snapshot.toImage(...).then is not a function(…)

toImage() is returning an EventEmitter.

What am I missing?

[gramster]

Ah, I see. I need to use ...toImage(...).once('success', function(url) { ...})

[ifll]

I think that for the user it would be really interesting to be able to choose the image size. But also it could be too much features on the plot and reduce simplicity...

I would suggest that the coder who is buiding the plot could choose if the users (the ones who will be watching the plot) are capable to change or not the PNG image from the plot.

To do so I would suggest to add inside the layout variable an option which involves the modebar, and where it could be such a variable like "snapshotsize" which could admit a vector including a fixed size: snapshotsize = [1000 1000] or either the auto option snapshotsize = "auto"

Regarding the "auto" functionality I would suggest that a dialog box appears on the plot allowing to choose the dimension of it. Somehow similar to the message box which appears when you click the snapshot button and it tells you that Taking snapshot - this may take a few seconds

With this implementation the current way that snapshots are being done right now can be kept (as the coder can decide the output size) but also the new feature of being able to choose the plot size can be implemented.