Re: [matplotlib-devel] Comparing pdf output in tests

[Andrew S. <str...@as...>]

John Hunter wrote:
> On Wed, Sep 23, 2009 at 12:56 PM, Andrew Straw <str...@as...> wrote:
>   
>> John Hunter wrote:
>>     
>>> On Wed, Sep 23, 2009 at 12:42 PM, Andrew Straw <str...@as...> wrote:
>>>
>>>
>>>       
>>>> Sorry, I should have been more clear. I was thinking that the
>>>> image_compare() decorator would call the test function multiple times,
>>>> having switched the backend between invocations. Thus, the call to
>>>> savefig() would continue not to explicitly set the extension. I've
>>>> quickly modified the source to reflect my idea, but I haven't had a
>>>> chance to flesh it out or test it. It should show the idea, though. See
>>>> attached.
>>>>
>>>>         
>>> Why not have the decorator pass the extension in to the test funcs --
>>> agg can print to pdf, ps, svg and png
>>>
>>>       
>> I'm not sure what you're suggesting. Presumably if we're driving agg OK
>> to draw .png, it will also draw .pdf OK (or does it have a pdf vector
>> backend independent of the MPL pdf backend that we want to test separately?)
>>     
>
> No, it doesn't have a separate backend, but the backend_agg figure
> canvas savefig method knows how to create FigureCanvasPDF etc to use
> that backend to write the file w/o having to switch the default
> backend with all the attendant hassles.  So if you are using *Agg, and
> do
>
>   savefig(somefile.pdf)
>
> agg will load the native pdf backend and use it.  So I was envisioning
>
> def test_something(ext):
>    make_plot
>    fig.savefig('myfile.%s'%ext)
>
> and having the decorator pass in the extensions it wants one-by-one
>   
I see. Is there something like
backend_agg.set_default_savefig_extension()? That would achieve both of
our goals. So maybe if it doesn't exist it would be easy to add in?

-Andrew