Scale params to match existing appearance

takimata · takimata · commit 08d1aa60283b · 2021-08-23T09:59:52.000+02:00
diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
@@ -611,13 +611,16 @@ def _print_pgf_path(self, gc, path, transform, rgbFace=None):
             # -> Use "randomness" as PRNG seed to allow the user to force the
             # same shape on multiple sketched lines
             scale, length, randomness = sketch_params
+            # make PGF output visually similar to matplotlib's sketched lines
+            adjustment_a = 0.5
+            adjustment_b = 2
             if scale is not None:
                 # PGF guarantees that repeated loading is a no-op
                 writeln(self.fh, r"\usepgfmodule{decorations}")
                 writeln(self.fh, r"\usepgflibrary{decorations.pathmorphing}")
                 writeln(self.fh, r"\pgfkeys{/pgf/decoration/.cd, "
-                        f"segment length = {(length * f):f}in, "
-                        f"amplitude = {(scale * f):f}in}}")
+                        f"segment length = {(length * f * adjustment_a):f}in, "
+                        f"amplitude = {(scale * f * adjustment_b):f}in}}")
                 writeln(self.fh, f"\\pgfmathsetseed{{{int(randomness)}}}")
                 writeln(self.fh, r"\pgfdecoratecurrentpath{random steps}")
 
diff --git a/lib/matplotlib/tests/test_backend_pgf.py b/lib/matplotlib/tests/test_backend_pgf.py
@@ -357,7 +357,7 @@ def test_sketch_params():
 \usepgfmodule{decorations}%
 \usepgflibrary{decorations.pathmorphing}%
 \pgfkeys{/pgf/decoration/.cd, """ \
-    r"""segment length = 0.300000in, amplitude = 0.050000in}%
+    r"""segment length = 0.150000in, amplitude = 0.100000in}%
 \pgfmathsetseed{42}%
 \pgfdecoratecurrentpath{random steps}%
 \pgfusepath{stroke}%"""
