Default setting of figure transparency in NbAgg is a performance problem

[mdboom]

I missed the implications of #3552 when it went through.

If any part of the plot image is transparent, a full image frame is sent in order to make sure there isn't any ghosting. The default value of nbagg.transparent == True unfortunately means that full images are always sent for every frame. This results in lower framerates and flickering.

I can workaround this by setting figure.facecolor: white and nbagg.transparent: False, but I wonder if we shouldn't make this the default. 2.0 might be a good opportunity to make figure.facecolor: white the default for every backend anyway, which does generally look more modern.

It does mean it IPython ever changes their style to something on a non-white background things may not look as nice, but we'll cross that when we get there.

Cc: @pelson

[WeatherGod]

I think the reason why that setting was set that way was to match the
appearance for the inline images. Quite honestly, I hate that, as it has
bitten me multiple times when I copy an image over from a notebook to
PowerPoint...

On Fri, Nov 6, 2015 at 9:53 AM, Michael Droettboom <notifications@github.com

wrote:

I missed the implications of #3552
#3552 when it went through.

If any part of the plot image is transparent, a full image frame is sent
in order to make sure there isn't any ghosting. The default value of nbagg.transparent
== True unfortunately means that full images are always sent for every
frame. This results in lower framerates and flickering.

I can workaround this by setting figure.facecolor: white and nbagg.transparent:
False, but I wonder if we shouldn't make this the default. 2.0 might be a
good opportunity to make figure.facecolor: white the default for every
backend anyway, which does generally look more modern.

It does mean it IPython ever changes their style to something on a
non-white background things may not look as nice, but we'll cross that when
we get there.

Cc: @pelson https://github.com/pelson

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Reply to this email directly or view it on GitHub
#5419.

[mdboom]

I think the reason why that setting was set that way was to match the
appearance for the inline images.

Ok -- that at least makes some sense. But wouldn't setting the background to white for inline images also be one way to fix that?

Quite honestly, I hate that, as it has bitten me multiple times when I copy an image over from a notebook to PowerPoint...

Meaning you hate that the inline images are transparent or vice versa?

[WeatherGod]

Correct, setting the background to white for inline images would fix that,
but isn't that handled by IPython? And yes, I hate transparent images in
general.

On Fri, Nov 6, 2015 at 10:33 AM, Michael Droettboom <
notifications@github.com> wrote:

I think the reason why that setting was set that way was to match the
appearance for the inline images.

Ok -- that at least makes some sense. But wouldn't setting the background
to white for inline images also be one way to fix that?

Quite honestly, I hate that, as it has bitten me multiple times when I
copy an image over from a notebook to PowerPoint...

Meaning you hate that the inline images are transparent or vice versa?

—
Reply to this email directly or view it on GitHub
#5419 (comment)
.

[mdboom]

Yes -- I think IPython sets the transparent background on inline images. We can always lobby them to stop if that makes sense... ;)

[jenshnielsen]

Yes it's set here https://github.com/ipython/ipykernel/blob/master/ipykernel/pylab/config.py

[efiring]

This sounds related to a problem I just ran into with master, and with %matplotlib notebook: saving to a png with fig.savefig, I could not find a way to make the png figure background white instead of transparent. Has anyone else seen this? To get around it I had to switch to using %matplotlib inline.

[pelson]

If any part of the plot image is transparent, a full image frame is sent in order to make sure there isn't any ghosting.

We could be more sophisticated with the solution - we could send over only the semi-transparent pixels as a separate message and clear those pixels before applying them on the JS side.

Either way, I'm 👍 on producing white borders by default - for both nbagg and all other backends. I've disliked the fact that we have a savefig.transparent setting which changes how a figure looks between interactivity and savefig for some time, and this would go some way to fixing that.