Re: [Matplotlib-users] Printing Graphs and Image Processing Operations

[Wayne W. <sie...@sb...>]

Thanks. I'll keep this in mind when I get to the point when I'm ready to 
consider it as part of a program I'm writing. Someone in Image-SIG sent 
me a module he wrote that might be helpful too.

Michael Droettboom wrote:
> Wayne Watson wrote:
>> I've used MPL a bit, and am wondering if there's a facility for 
>> sending graphic images to a printer, or putting them in some format 
>> like png?   I don't necessarily want the graphics to appear in a 
>> window, but would like to print them directly once they are ready. 
>> Can one put in a page feed, so that images don't all fall on the same 
>> page or cut across pages?
>>   
> You can use one of the non-GUI backends to generate plots in a number 
> of formats, including PNG, PDF, PS and SVG.  See this:
>
> http://matplotlib.sourceforge.net/faq/installing_faq.html#backends
>
> The PDF backend is the only one I'm aware of that supports multiple 
> pages.  This is the docstring for PdfPages:
>
>    A multi-page PDF file.
>
>    Use like this::
>
>        # Initialize:
>        pp = PdfPages('foo.pdf')
>
>        # As many times as you like, create a figure fig, then either:
>        fig.savefig(pp, format='pdf') # note the format argument!
>        # or:
>        pp.savefig(fig)
>
>        # Once you are done, remember to close the object:
>        pp.close()
>
>    (In reality PdfPages is a thin wrapper around PdfFile, in order to
>    avoid confusion when using savefig and forgetting the format
>    argument.)
>
>> Is there any image processing operation available to do simple 
>> operations like dark subtract or stack different images on one other 
>> to produce composites of several images?  Maybe Python has such a 
>> facility that's already available as a library?
>>
>>   
> Matplotlib doesn't have a very strong set of these things built-in 
> (though some things are possible with the image support in the image 
> module).  You can also get an rgb buffer of the figure (when using the 
> Agg backend), eg. (where 'fig' is the figure object):
>
>   fig.canvas.get_renderer().tostring_rgb()
>
> This is a string of 24-bit rgb triples, which can be converted to the 
> Numpy array for arithmetical processing, or converted to a Python 
> Imaging Library Image object.
>
> Mike
>

-- 
           Wayne Watson (Watson Adventures, Prop., Nevada City, CA)

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