A similar approach as the last one should work, the problem I was having is
that to print the binary string from python you have to decode it, and
latin-1 seems close to right, but it puts a bunch of extra bytes in it that
lead to a bad png file. I feel like this worked in Python2 with StringIO,
but not in Python3 with BytesIO.



John

-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Sat, Jun 8, 2019 at 6:52 AM Roger Mason <rmason@mun.ca> wrote:

> Hello John,
>
> John Kitchin <jkitchin@andrew.cmu.edu> writes:
>
> > you probably figured out the "import io" and "f = io..." line are not
> > necessary here.
>
> Indeed.
>
> > I couldn't figure out a reasonable way to use :results graphics link
> > that didn't result in repeating the filename more than desired. These
> > also both work, but seem to both require repeating the filename twice.
> >
> > #+BEGIN_SRC python :results graphics link :var fname="test.png" :file
> "test.png"
> > import matplotlib.pyplot as plt
> >
> > plt.plot([1, 2, 3, 1])
> > plt.savefig(fname)
> > #+END_SRC
> >
> > #+BEGIN_SRC python :results graphics link :file "test.png"
> > import matplotlib.pyplot as plt
> >
> > plt.plot([1, 2, 3])
> > plt.savefig("test.png")
> > #+END_SRC
> >
> > Something like this should work, but there seem to be some extra bytes
> > getting put in the png file from the decoding, and latin-1 is the only
> > one I can get to work. If anyone knows how to get this to work, I am
> > interested in seeing it!
> >
> > #+BEGIN_SRC python :results value :file "io.png"
> > import matplotlib.pyplot as plt
> > import io
> > buf = io.BytesIO()
> >
> > plt.plot([1, 2, 3])
> > plt.savefig(buf, format='png')
> >
> > s = buf.getvalue()
> > return s.decode('latin-1')
> > #+END_SRC
> >
> >
> > In general though, all of these are much more work than using
> > ob-ipython, which just puts images in the buffer for you.
>
> I will investigate that, thanks for the tip.  I began this bit of work
> using gnuplot for making x-y plots, but I find that gnuplot syntax gets
> messy for anything but simple data.  I am not a particular fan
> of python so I'm also looking into guile & racket for plotting.
>
> Thanks for your help, it is much appreciated.
>
> Roger
>