Merge pull request matplotlib#19525 from anntzer/pdfgroup

Don't create page transparency group in pdf output (for pdftex compat).

Author: timhoffm

lib/matplotlib/backends/backend_pdf.py

@@ -728,9 +728,6 @@ def newPage(self, width, height):
                    'Resources': self.resourceObject,
                    'MediaBox': [0, 0, 72 * width, 72 * height],
                    'Contents': contentObject,
-                   'Group': {'Type': Name('Group'),
-                             'S': Name('Transparency'),
-                             'CS': Name('DeviceRGB')},
                    'Annots': annotsObject,
                    }
         pageObject = self.reserveObject('page')
@@ -740,8 +737,10 @@ def newPage(self, width, height):
 
         self.beginStream(contentObject.id,
                          self.reserveObject('length of content stream'))
-        # Initialize the pdf graphics state to match the default mpl
-        # graphics context: currently only the join style needs to be set
+        # Initialize the pdf graphics state to match the default Matplotlib
+        # graphics context (colorspace and joinstyle).
+        self.output(Name('DeviceRGB'), Op.setcolorspace_stroke)
+        self.output(Name('DeviceRGB'), Op.setcolorspace_nonstroke)
         self.output(GraphicsContextPdf.joinstyles['round'], Op.setlinejoin)
 
         # Clear the list of annotations for the next page