Re: [matplotlib-devel] PNG transparency

[Michael D. <md...@st...>]

John wrote:

"I believe the unspoken consensus was it is easy to set the alpha on
the figurePatch and axesPatch so a global alpha was unneccessary."


It still might be convenient to make this an option on savefig.  Sure it's only a few lines of code, but not necessarily obvious lines of code.

Waiting to hear back from Nils as to whether this is really what he 
wants, though.

Cheers,
Mike

Michael Droettboom wrote:
> Nils,
>
> I saw your bump about this transparency issue.  Before moving forward 
> on this, I'd like to know what your use case is.  I've attached a 
> mock-up example.  On the left is the effect of changing the alpha 
> value of everything to 50% (what you and Christopher had suggested).  
> But it seems to me what you really want is on the right -- making only 
> the figure and axes patch fully-transparent.  This is what one would 
> want, for example, when putting a plot on the colored background of a 
> webpage.  I don't understand why anyone would want the one on the 
> left, but if you can provide a use case for it, it should be 
> implementable.
>
> Cheers,
> Mike
>
> Michael Droettboom wrote:
>> Of course, this depends on what you mean by transparency.  If you 
>> mean to change the alpha of the entire PNG, then yes, the global 
>> parameter (or postprocessing) is the way to go.  But I'm not sure how 
>> useful that is -- that will still lighten things behind the figure 
>> and axes patch.
>> A more useful option, IMHO, would be to just make the figure patch 
>> and axes patch fully transparent and leave everything else "as is".  
>> That avoids the "white box on a colored background" problem.
>>
>> Cheers,
>> Mike
>>
>> Christopher Barker wrote:
>>  
>>> Nils Wagner wrote:
>>>      
>>>>   "John Hunter" <jd...@gm...> wrote:
>>>>          
>>>>> I wonder if we should support a global rc alpha....
>>>>>               
>>> I'd make it an optional parameter to savefig(), but I like the idea.
>>>
>>> Of course one could pretty easily post-process it as well.
>>>
>>> -CHB
>>>
>>>
>>>       
>>
>>   
>
>
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-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA