Reduce numerical precision in Type 1 fonts

jkseppan · jkseppan · commit 013d508d24ac · 2020-07-27T10:12:12.000+03:00
Fixes #16087
diff --git a/lib/matplotlib/tests/test_type1font.py b/lib/matplotlib/tests/test_type1font.py
@@ -29,7 +29,7 @@ def test_Type1Font():
         '+ /FontName /CMR10_Slant_1000 def',
          # Alters FontMatrix
          '- /FontMatrix [0.001 0 0 0.001 0 0 ]readonly def',
-         '+ /FontMatrix [0.001 0.0 0.001 0.001 0.0 0.0]readonly def',
+         '+ /FontMatrix [0.001 0 0.001 0.001 0 0]readonly def',
          # Alters ItalicAngle
          '-  /ItalicAngle 0 def',
          '+  /ItalicAngle -45.0 def'):
@@ -47,5 +47,23 @@ def test_Type1Font():
         '+ /FontName /CMR10_Extend_500 def',
          # Alters FontMatrix
          '- /FontMatrix [0.001 0 0 0.001 0 0 ]readonly def',
-         '+ /FontMatrix [0.0005 0.0 0.0 0.001 0.0 0.0]readonly def'):
+         '+ /FontMatrix [0.0005 0 0 0.001 0 0]readonly def'):
         assert line in diff, 'diff to condensed font must contain %s' % line
+
+
+def test_overprecision():
+    # We used to output too many digits in FontMatrix entries and
+    # ItalicAngle, which could make Type-1 parsers unhappy.
+    filename = os.path.join(os.path.dirname(__file__), 'cmr10.pfb')
+    font = t1f.Type1Font(filename)
+    slanted = font.transform({'slant': .167})
+    lines = slanted.parts[0].decode('ascii').splitlines()
+    matrix, = [line[line.index('[')+1:line.index(']')]
+               for line in lines if '/FontMatrix' in line]
+    angle, = [word
+              for line in lines if '/ItalicAngle' in line
+              for word in line.split() if word[0] in '-0123456789']
+    # the following used to include 0.00016700000000000002
+    assert matrix == '0.001 0 0.000167 0.001 0 0'
+    # and here we had -9.48090361795083
+    assert angle == '-9.4809'
diff --git a/lib/matplotlib/type1font.py b/lib/matplotlib/type1font.py
@@ -251,7 +251,10 @@ def fontname(name):
             return result
 
         def italicangle(angle):
-            return b'%a' % (float(angle) - np.arctan(slant) / np.pi * 180)
+            return b'%a' % round(
+                float(angle) - np.arctan(slant) / np.pi * 180,
+                5
+            )
 
         def fontmatrix(array):
             array = array.lstrip(b'[').rstrip(b']').split()
@@ -265,10 +268,9 @@ def fontmatrix(array):
             newmatrix = np.dot(modifier, oldmatrix)
             array[::2] = newmatrix[0:3, 0]
             array[1::2] = newmatrix[0:3, 1]
-            # Not directly using `b'%a' % x for x in array` for now as that
-            # produces longer reprs on numpy<1.14, causing test failures.
-            as_string = '[' + ' '.join(str(x) for x in array) + ']'
-            return as_string.encode('latin-1')
+            return (
+                '[' + ' '.join(f'{x:.5g}' for x in array) + ']'
+            ).encode('ascii')
 
         def replace(fun):
             def replacer(tokens):
