Re: [matplotlib-devel] animation in SVG

[Benjamin R. <ben...@ou...>]

It sounds like you are on the right path, and you do raise some interesting
points. I would certainly be open to accepting improvements to the
animation framework to facilitate this work. As for the gray vs. white
backgrounds, I am not all that familiar with how that is handled, but IIRC,
the non-interactive backends obtain the background color from the rcparams.

I would love to see a PR for your efforts so far. An SVG animator would
also be valuable as a way to add unit-tests to the animation framework
since it would be easier to do comparisons, I would think.


On Fri, Feb 27, 2015 at 11:09 AM, tbhartman <tbh...@gm...> wrote:

> I trust this is an appropriate place; this is my first time on this
> listserv.
>
> I want to add the ability to export an animation in SVG format so that I
> have a vectorized animation.  From what I've been able to discern, this
> hasn't been done yet.  I may have many questions related to this, so if
> someone is familiar with this section of the code and would be able to
> answer additional questions in the future, please let me know.
>
> My first hurdle is how to extract each frame of the animation.  I believe I
> need to make a new class and inherit MovieWriter.  However, MovieWriter is
> setup to write an image to a file for each frame, then stitch those images
> together (through a pipe to an external tool).  But in order to add
> animation to the SVG, it will be much easier for me to have an XML tree as
> an object for each frame, rather than an XML file, so that I do not need to
> re-parse the XML.
>
> Here is where I am at:
> * I've modified backend_svg.py:
>   - an XMLBuilder class now builds the tree from the renderer (previously,
> the XML data was written directly through XMLWriter)
>   - currently, I have the svg backend (mostly) backward compatible so that
> I
> can write images to file in the normal way.  I have not run the example
> tests yet, but need to eventually.
>   - I added a draw method to FigureCanvasSVG which returns the XML tree
> * I've modified animation.py:
>   - added SVGWriter class which inherits MovieWriter
>   - SVGWriter modifies setup method so that an external process is not
> started
>   - SVGWriter.grab_frame method grabs the XML tree (rather than printing to
> a file) via FigureCanvasSVG.draw
>   - SVGWriter.cleanup goes through the XML trees and adds 'set' XML
> elements
> to create the animation
>     * basically I copy the main group of each frame to a new XML tree and
> make it's "opacity" CSS attribute 1 for the duration of that frame.  It is
> a
> hack to get the rest working...I'd like to actually go into the tree and
> only change the data that changes in each frame.
>
> I am at the point where I can get an SVG animation out of the moviewriter
> example at:
>
> http://matplotlib.org/examples/animation/moviewriter.html
>
> However, FigureCanvas.draw does not seem the appropriate place for this.
> Case in point, the background is the default gray rather than white (which
> you get if you savefig).  Any thoughts on the best way to do this?
>
> -Tim
>
>
>
>
> --
> View this message in context:
> http://matplotlib.1069221.n5.nabble.com/animation-in-SVG-tp45021.html
> Sent from the matplotlib - devel mailing list archive at Nabble.com.
>
>
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