Merge pull request #2907 from munkm/mpl-backport

Reissue #2800: backport #2754 to stable

yt/utilities/png_writer.py

@@ -10,28 +10,37 @@
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
-import matplotlib._png as _png
 from yt.extern.six import PY2
 
 if PY2:
     from cStringIO import StringIO
 else:
     from io import BytesIO as StringIO
 
-def call_png_write_png(buffer, width, height, fileobj, dpi):
-    _png.write_png(buffer, fileobj, dpi)
+try:
+    # matplotlib switched from an internal submodule _png to using pillow (PIL)
+    # between v3.1.0 and v3.3.0
+    # So PIL should be available on any system where matplotlib._png doesn't exist
+    import matplotlib._png as _png
+except ImportError:
+    from PIL import Image
+
+
+def call_png_write_png(buffer, fileobj, dpi):
+    try:
+        _png.write_png(buffer, fileobj, dpi)
+    except NameError:
+        Image.fromarray(buffer).save(fileobj, dpi=(dpi, dpi), format="png")
+
 
 def write_png(buffer, filename, dpi=100):
-    width = buffer.shape[1]
-    height = buffer.shape[0]
     with open(filename, "wb") as fileobj:
-        call_png_write_png(buffer, width, height, fileobj, dpi)
+        call_png_write_png(buffer, fileobj, dpi)
+
 
-def write_png_to_string(buffer, dpi=100, gray=0):
-    width = buffer.shape[1]
-    height = buffer.shape[0]
+def write_png_to_string(buffer, dpi=100):
     fileobj = StringIO()
-    call_png_write_png(buffer, width, height, fileobj, dpi)
+    call_png_write_png(buffer, fileobj, dpi)
     png_str = fileobj.getvalue()
     fileobj.close()
     return png_str