[ACCEPTED]-Returning Matplotlib image as string-matplotlib

Accepted answer
Score: 18

Django's HttpResponse object supports file-like API 2 and you can pass a file-object to savefig.

response = HttpResponse(mimetype="image/png")
# create your image as usual, e.g. pylab.plot(...)
pylab.savefig(response, format="png")
return response

Hence, you 1 can return the image directly in the HttpResponse.

Score: 6

what about cStringIO?

import pylab
import cStringIO
output = cStringIO.StringIO()
pylab.savefig('test.png', dpi=75)
pylab.savefig(output, dpi=75)
print output.getvalue() == open('test.png', 'rb').read() # True


Score: 2

There is a recipe in the Matplotlib Cookbook that does exactly 13 this. At its core, it looks like:

def simple(request):
    from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
    from matplotlib.figure import Figure

    ax.plot(range(10), range(10), '-')
    return response

Put that 12 in your views file, point your URL to it, and 11 you're off and running.

Edit: As noted, this 10 is a simplified version of a recipe in the 9 cookbook. However, it looks like there 8 is a difference between calling print_png and savefig, at 7 least in the initial test that I did. Calling 6 fig.savefig(response, format='png') gave an image with that was larger and 5 had a white background, while the original 4 canvas.print_png(response) gave a slightly smaller image with a grey 3 background. So, I would replace the last 2 few lines above with:

    fig.savefig(response, format='png')
    return response

You still need to have 1 the canvas instantiated, though.

Score: 0

Employ ducktyping and pass a object of your 3 own, in disguise of file object

class MyFile(object):
    def __init__(self):
        self._data = ""
    def write(self, data):
        self._data += data

myfile = MyFile()
print myfile._data

you can use 2 myfile = StringIO.StringIO() instead in 1 real code and return data in reponse e.g.

output = StringIO.StringIO()
contents = output.getvalue()
return HttpResponse(contents , mimetype="image/png")

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