Can matplotlib add metadata to saved figures?

Question

I want to be able to ascertain the provenance of the figures I create using matplotlib, i.e. to know which version of my code and data created these figures. (See this essay for more on provenance.)

I imagine the most straightforward approach would be to add the revision numbers of the code and data to the metadata of the saved figures, or as comments in a postscript file for example.

Is there any easy way to do this in Matplotlib? The savefig function doesn't seem to be capable of this but has someone come up with a workable solution?

Answer 1

I don't know of a way using matplotlib, but you can add metadata to png's with PIL:

f = "test.png"
METADATA = {"version":"1.0", "OP":"ihuston"}

# Create a sample image
import pylab as plt
import numpy as np
X = np.random.random((50,50))
plt.imshow(X)
plt.savefig(f)

# Use PIL to save some image metadata
from PIL import Image
from PIL import PngImagePlugin

im = Image.open(f)
meta = PngImagePlugin.PngInfo()

for x in METADATA:
    meta.add_text(x, METADATA[x])
im.save(f, "png", pnginfo=meta)

im2 = Image.open(f)
print im2.info

This gives:

{'version': '1.0', 'OP': 'ihuston'}