assertImagesEqual : Add maxDifferenceGreater and maxDifferenceLess

This allows using a different tolerance for pixels where A > B and pixels where A < B.

python/GafferImageTest/ConstantTest.py

@@ -208,5 +208,33 @@ def testLayerAffectsChannelNames( self ) :
 
 		self.assertTrue( c["out"]["channelNames"] in set( [ x[0] for x in cs ] ) )
 
+	def testAssertImagesEqual( self ) :
+
+		a = GafferImage.Constant()
+		a["color"].setValue( imath.Color4f( 0.5 ) )
+
+		b = GafferImage.Constant()
+		b["color"].setValue( imath.Color4f( 0.5 ) )
+
+		self.assertImagesEqual( a["out"], b["out"] )
+
+		a["color"].setValue( imath.Color4f( 0.75 ) )
+
+		with self.assertRaisesRegex( AssertionError, "0.25 not less than or equal to 0.0 : Channel R" ) :		
+			self.assertImagesEqual( a["out"], b["out"] )
+
+		self.assertImagesEqual( a["out"], b["out"], maxDifference = 0.25 )
+
+		self.assertImagesEqual( a["out"], b["out"], maxDifferenceGreater = 0.25 )
+		with self.assertRaisesRegex( AssertionError, "-0.25 not greater than or equal to -0.0 : Channel R" ) :		
+			self.assertImagesEqual( a["out"], b["out"], maxDifferenceLess = 0.25 )
+
+		b["color"].setValue( imath.Color4f( 1.0 ) )
+
+		self.assertImagesEqual( a["out"], b["out"], maxDifferenceLess = 0.25 )
+		with self.assertRaisesRegex( AssertionError, "0.25 not less than or equal to 0.0 : Channel R" ) :		
+			self.assertImagesEqual( a["out"], b["out"], maxDifferenceGreater = 0.25 )
+
+
 if __name__ == "__main__":
 	unittest.main()

python/GafferImageTest/ImageTestCase.py

@@ -98,7 +98,7 @@ def assertImageHashesEqual( self, imageA, imageB ) :
 						tileOrigin.x += GafferImage.ImagePlug.tileSize()
 					tileOrigin.y += GafferImage.ImagePlug.tileSize()
 
-	def assertImagesEqual( self, imageA, imageB, maxDifference = 0.0, ignoreMetadata = False, ignoreDataWindow = False, ignoreChannelNamesOrder = False, ignoreViewNamesOrder = False, metadataBlacklist = [] ) :
+	def assertImagesEqual( self, imageA, imageB, maxDifference = 0.0, ignoreMetadata = False, ignoreDataWindow = False, ignoreChannelNamesOrder = False, ignoreViewNamesOrder = False, metadataBlacklist = [], maxDifferenceGreater = None, maxDifferenceLess = None ) :
 
 		self.longMessage = True
 
@@ -107,6 +107,11 @@ def assertImagesEqual( self, imageA, imageB, maxDifference = 0.0, ignoreMetadata
 		else :
 			self.assertEqual( set( imageA.viewNames() ), set( imageB.viewNames() ) )
 
+		if maxDifferenceGreater is None:
+			maxDifferenceGreater = maxDifference
+		if maxDifferenceLess is None:
+			maxDifferenceLess = maxDifference
+
 		for view in imageA.viewNames():
 
 			with Gaffer.Context( Gaffer.Context.current() ) as context :
@@ -141,7 +146,6 @@ def assertImagesEqual( self, imageA, imageB, maxDifference = 0.0, ignoreMetadata
 					difference = GafferImage.Merge()
 					difference["in"][0].setInput( imageA )
 					difference["in"][1].setInput( imageB )
-					difference["operation"].setValue( GafferImage.Merge.Operation.Difference )
 
 					unionDataWindow = imath.Box2i( dataWindowA )
 					unionDataWindow.extendBy( dataWindowB )
@@ -153,7 +157,15 @@ def assertImagesEqual( self, imageA, imageB, maxDifference = 0.0, ignoreMetadata
 					for channelName in imageA["channelNames"].getValue() :
 
 						stats["channels"].setValue( IECore.StringVectorData( [ channelName ] * 4 ) )
-						self.assertLessEqual( stats["max"]["r"].getValue(), maxDifference, "Channel {0}".format( channelName ) )
+						difference["operation"].setValue( GafferImage.Merge.Operation.Difference )
+						self.assertLessEqual(
+							stats["max"]["r"].getValue(), max( maxDifferenceGreater, maxDifferenceLess ),
+							"Channel {0}".format( channelName )
+						)
+						if maxDifferenceGreater != maxDifferenceLess:
+							difference["operation"].setValue( GafferImage.Merge.Operation.Subtract )
+							self.assertLessEqual( stats["max"]["r"].getValue(), maxDifferenceLess, "Channel {0}".format( channelName ) )
+							self.assertGreaterEqual( stats["min"]["r"].getValue(), -maxDifferenceGreater, "Channel {0}".format( channelName ) )
 					# Access the tiles, because this will throw an error if the sample offsets are bogus
 					GafferImage.ImageAlgo.tiles( imageA )
 					GafferImage.ImageAlgo.tiles( imageB )