#!/usr/bin/python

# Creates a PNG histogram of the focal lengths of the images on the command
# line, called "fl-hist.png", in the current directory.

import os
import os.path
import subprocess
import sys

import matplotlib
matplotlib.use("cairo")
import matplotlib.pyplot as plt

OUTFILE = "fl-hist.png"

#if (os.path.exists(OUTFILE)):
#   print "%s exists, aborting" % (OUTFILE)
#   sys.exit(1)

focals = list()
for f in sys.argv[1:]:
   focal = os.popen("exiftool -FocalLength -b %s" % (f)).read()
   focal = int(round(float(focal)))
   print f, focal
   focals.append(focal)

if (len(focals) == 0):
   print "no files given, aborting"
   sys.exit(1)

#focals.sort()
bins = range(min(focals), max(focals) + 1)
#for focal in focals:
#   if (focal not in bins):
#      bins.append(focal)
#print bins

plt.figure(figsize=(6,4.5))
plt.hist(focals,
         bins=bins,
         align="left",
         edgecolor="blue")
plt.xlabel("Focal length (mm)")
plt.ylabel("Number of photos")
plt.axis(xmin=10, xmax=(max(focals) + 5))
plt.savefig("fl-hist.png", format="png")