Deterministic svg

doc/api/backend_svg_api.rst

@@ -0,0 +1,7 @@
+
+:mod:`matplotlib.backends.backend_svg`
+======================================
+
+.. automodule:: matplotlib.backends.backend_svg
+   :members:
+   :show-inheritance:

doc/api/index_backend_api.rst

@@ -12,6 +12,7 @@ backends
    backend_qt5agg_api.rst
    backend_wxagg_api.rst
    backend_pdf_api.rst
+   backend_svg_api.rst
 ..   backend_webagg.rst
    dviread.rst
    type1font.rst

doc/users/whats_new/rcparams.rst

@@ -0,0 +1,5 @@
+Added ``svg.hashsalt`` key to rcParams
+```````````````````````````````````````
+If ``svg.hashsalt`` is ``None`` (which it is by default), the svg backend uses ``uuid4`` to generate the hash salt.
+If it is not ``None``, it must be a string that is used as the hash salt instead of ``uuid4``.
+This allows for deterministic SVG output.

lib/matplotlib/axes/_base.py

@@ -1,10 +1,11 @@
 from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
+from collections import OrderedDict
+
 from matplotlib.externals import six
 from matplotlib.externals.six.moves import xrange
 
-from collections import OrderedDict
 import itertools
 import warnings
 import math
@@ -33,7 +34,6 @@
 import matplotlib.image as mimage
 from matplotlib.offsetbox import OffsetBox
 from matplotlib.artist import allow_rasterization
-from matplotlib.cbook import iterable, index_of
 from matplotlib.rcsetup import cycler
 
 rcParams = matplotlib.rcParams

lib/matplotlib/backends/backend_svg.py

@@ -1,12 +1,13 @@
 from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
+from collections import OrderedDict
+
 from matplotlib.externals import six
 from matplotlib.externals.six.moves import xrange
 from matplotlib.externals.six import unichr
 
 import os, base64, tempfile, gzip, io, sys, codecs, re
-from collections import OrderedDict
 
 import numpy as np
 
@@ -316,7 +317,10 @@ def _write_default_style(self):
 
     def _make_id(self, type, content):
         content = str(content)
-        salt = str(uuid.uuid4())
+        if rcParams['svg.hashsalt'] is None: 
+            salt = str(uuid.uuid4())
+        else:
+            salt = rcParams['svg.hashsalt']
         if six.PY3:
             content = content.encode('utf8')
             salt = salt.encode('utf8')
@@ -840,7 +844,7 @@ def draw_image(self, gc, x, y, im, dx=None, dy=None, transform=None):
         if rcParams['svg.image_inline']:
             bytesio = io.BytesIO()
             _png.write_png(np.array(im)[::-1], bytesio)
-            oid = oid or self._make_id('image', bytesio)
+            oid = oid or self._make_id('image', bytesio.getvalue())
             attrib['xlink:href'] = (
                 "data:image/png;base64,\n" +
                 base64.b64encode(bytesio.getvalue()).decode('ascii'))

lib/matplotlib/rcsetup.py

@@ -166,6 +166,16 @@ def validate_float_or_None(s):
         raise ValueError('Could not convert "%s" to float or None' % s)
 
 
+def validate_string_or_None(s):
+    """convert s to string or raise"""
+    if s is None:
+        return None
+    try:
+        return six.text_type(s)
+    except ValueError:
+        raise ValueError('Could not convert "%s" to string' % s)
+
+
 def validate_dpi(s):
     """confirm s is string 'figure' or convert s to float or raise"""
     if s == 'figure':
@@ -1165,6 +1175,7 @@ def validate_hist_bins(s):
     # True to save all characters as paths in the SVG
     'svg.embed_char_paths': [True, deprecate_svg_embed_char_paths],
     'svg.fonttype':         ['path', validate_svg_fonttype],
+    'svg.hashsalt':         [None, validate_string_or_None],
 
     # set this when you want to generate hardcopy docstring
     'docstring.hardcopy': [False, validate_bool],

lib/matplotlib/tests/test_backend_svg.py

@@ -119,6 +119,48 @@ def test_bold_font_output_with_none_fonttype():
     ax.set_title('bold-title', fontweight='bold')
 
 
+def _test_determinism(filename):
+    # This function is mostly copy&paste from "def test_visibility"
+    # To require no GUI, we use Figure and FigureCanvasSVG
+    # instead of plt.figure and fig.savefig
+    from matplotlib.figure import Figure
+    from matplotlib.backends.backend_svg import FigureCanvasSVG
+    from matplotlib import rc
+    rc('svg', hashsalt='asdf')
+
+    fig = Figure()
+    ax = fig.add_subplot(111)
+
+    x = np.linspace(0, 4 * np.pi, 50)
+    y = np.sin(x)
+    yerr = np.ones_like(y)
+
+    a, b, c = ax.errorbar(x, y, yerr=yerr, fmt='ko')
+    for artist in b:
+        artist.set_visible(False)
+
+    FigureCanvasSVG(fig).print_svg(filename)
+
+
+@cleanup
+def test_determinism():
+    import os
+    import sys
+    from subprocess import check_call
+    from nose.tools import assert_equal
+    plots = []
+    for i in range(3):
+        check_call([sys.executable, '-R', '-c',
+                    'from matplotlib.tests.test_backend_svg '
+                    'import _test_determinism;'
+                    '_test_determinism("determinism.svg")'])
+        with open('determinism.svg', 'rb') as fd:
+            plots.append(fd.read())
+        os.unlink('determinism.svg')
+    for p in plots[1:]:
+        assert_equal(p, plots[0])
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule(argv=['-s', '--with-doctest'], exit=False)

lib/matplotlib/textpath.py

@@ -3,6 +3,8 @@
 from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
+from collections import OrderedDict
+
 from matplotlib.externals import six
 from matplotlib.externals.six.moves import zip
 
@@ -20,7 +22,6 @@
 from matplotlib.font_manager import FontProperties, get_font
 from matplotlib.transforms import Affine2D
 from matplotlib.externals.six.moves.urllib.parse import quote as urllib_quote
-from collections import OrderedDict
 
 
 class TextToPath(object):

matplotlibrc.template

@@ -505,6 +505,8 @@ backend      : %(backend)s
 #    'path': Embed characters as paths -- supported by most SVG renderers
 #    'svgfont': Embed characters as SVG fonts -- supported only by Chrome,
 #               Opera and Safari
+#svg.hashsalt : None           # if not None, use this string as hash salt
+                               # instead of uuid4
 
 # docstring params
 #docstring.hardcopy = False  # set this when you want to generate hardcopy docstring