WIP: patches/python: override py3 builtin round to keep py2 behavior.

And workaround safeimage impacted by this round2 patch.

bt5/erp5_safeimage/ExtensionTemplateItem/portal_components/extension.erp5.ERP5ZoomifyImage.py

@@ -16,6 +16,7 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 ##############################################################################
 
+import contextlib
 import os, sys, shutil, tempfile
 import io
 from zLOG import LOG,ERROR,INFO,WARNING
@@ -32,6 +33,29 @@ import base64
 from OFS.Folder import Folder
 from Products.ERP5Type.Utils import str2bytes
 
+
+import six
+# XXX zope4py3, we patch builtin round to keep python2 behavior
+# but this interfers with PIL, because python2 round sometimes
+# returns an int where python3 round is supposed to return a float.
+# This context manager swaps the implementation with the native
+# float on python3, which is NOT THREAD SAFE. Don't use it in
+# production, for now this makes the test pass 🤐.
+import Products.ERP5Type.patches.python
+@contextlib.contextmanager
+def native_round():
+  if six.PY3:
+    round_original = __builtins__['round']
+    try:
+      __builtins__['round'] = Products.ERP5Type.patches.python.round_native
+      yield
+    finally:
+      __builtins__['round'] = round_original
+  else:
+    # on python2 do nothing
+    yield
+
+
 class ZoomifyBase:
 
   _v_imageFilename = ''
@@ -179,8 +203,11 @@ class ZoomifyBase:
       saveFilename = root + str(tier) + '-' + str(row) +  ext
       if imageRow.mode != 'RGB':
         imageRow = imageRow.convert('RGB')
-      imageRow.save(os.path.join(tempfile.gettempdir(), saveFilename),
-                                                        'JPEG', quality=100)
+      with native_round():
+        imageRow.save(os.path.join(tempfile.gettempdir(), saveFilename),
+        # see https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html#jpeg-saving
+        # for quality, Values above 95 should be avoided;
+                                                        'JPEG', quality=95)
       if os.path.exists(os.path.join(tempfile.gettempdir(), saveFilename)):
         self.processRowImage(tier=tier, row=row)
       row += 1
@@ -256,9 +283,12 @@ class ZoomifyBase:
         # a bug was discovered when a row was exactly 1 pixel in height
         # this extra checking accounts for that
         if imageHeight > 1:
-          tempImage = imageRow.resize((imageWidth/2, imageHeight/2),
-                                                     PIL_Image.ANTIALIAS)
-          tempImage.save(os.path.join(tempfile.gettempdir(), root + str(tier)
+          tempImage = imageRow.resize(
+            (imageWidth//2, imageHeight//2),
+            PIL_Image.LANCZOS if six.PY3 else PIL_Image.ANTIALIAS,
+          )
+          with native_round():
+            tempImage.save(os.path.join(tempfile.gettempdir(), root + str(tier)
                                        + '-' + str(row) + ext))
           tempImage = None
       rowImage = None
@@ -537,7 +567,8 @@ class ERP5ZoomifyZopeProcessor(ZoomifyZopeProcessor):
       tile_group_id = self.getAssignedTileContainerName()
       tile_group=self.document[tile_group_id]
       tileImageData= io.BytesIO()
-      image.save(tileImageData, 'JPEG', quality=self.qualitySetting)
+      with native_round():
+        image.save(tileImageData, 'JPEG', quality=self.qualitySetting)
       tileImageData.seek(0)
       if tile_group is None:
         raise AttributeError('unable to fine tile group %r' % tile_group_id)

product/ERP5Type/patches/python.py

@@ -178,3 +178,43 @@ def patch_linecache():
 
 if sys.version_info[:3] < (3, ):
   patch_linecache()
+
+import decimal as _decimal
+
+
+def round2(number, ndigits=None):
+	"""
+	See Python 2 documentation.
+	Rounds a number to a given precision in decimal digits (default
+	0 digits). The result is a floating point number. Values are rounded
+	to the closest multiple of 10 to the power minus ndigits; if two
+	multiples are equally close, rounding is done away from 0.
+	ndigits may be negative.
+	"""
+	if ndigits is None:
+		ndigits = 0
+	elif hasattr(ndigits, '__index__'):
+		# any type with an __index__ method should be permitted as
+		# a second argument
+		ndigits = ndigits.__index__()
+
+	if ndigits < 0:
+		exponent = 10 ** (-ndigits)
+		quotient, remainder = divmod(number, exponent)
+		if remainder >= exponent//2 and number >= 0:
+			quotient += 1
+		return float(quotient * exponent)
+	else:
+		exponent = _decimal.Decimal('10') ** (-ndigits)
+
+		d = _decimal.Decimal.from_float(number).quantize(
+			exponent, rounding=_decimal.ROUND_HALF_UP)
+
+		return float(d)
+
+round_native = round
+
+if sys.version_info > (2, ):
+  __builtins__['round'] = round2
+  from AccessControl.ZopeGuards import safe_builtins
+  safe_builtins['round'] = round2