ImageStats : Fix handling of infinite values

If there are pixels with infinite value, we want that to be represented in the output.

Changes.md

@@ -45,6 +45,7 @@ Fixes
   - Stopped failed jobs jumping to the end of the Local Jobs UI.
   - Fixed message log update.
   - Fixed `Job.statistics()` errors on Windows, ensuring that a `pid` is always returned when available.
+- ImageStats : Fixed output of infinite values, which were previously being clamped.
 
 API
 ---

python/GafferImageTest/ImageStatsTest.py

@@ -36,6 +36,7 @@
 
 import os
 import unittest
+import math
 import imath
 
 import IECore
@@ -300,6 +301,31 @@ def testTaskCollaboration( self ) :
 
 		self.assertEqual( pm.plugStatistics( stats["__allStats" ] ).computeCount, 1 )
 
+	def testInf( self ) :
+
+		# Make an image with all `inf` values. We can't do this directly
+		# with a Constant because the inputs are clamped at float max,
+		# so we divide an image by zero to get what we want.
+
+		constant0 = GafferImage.Constant()
+		constant1 = GafferImage.Constant()
+		constant1["color"].setValue( imath.Color4f( 1 ) )
+
+		merge = GafferImage.Merge()
+		merge["in"][0].setInput( constant0["out"] )
+		merge["in"][1].setInput( constant1["out"] )
+		merge["operation"].setValue( merge.Operation.Divide )
+
+		# Since all values are `inf`, all outputs should be too.
+
+		stats = GafferImage.ImageStats()
+		stats["in"].setInput( merge["out"] )
+		stats["area"].setValue( stats["in"].format().getDisplayWindow() )
+
+		self.assertTrue( math.isinf( stats["max"][0].getValue() ) )
+		self.assertTrue( math.isinf( stats["min"][0].getValue() ) )
+		self.assertTrue( math.isinf( stats["average"][0].getValue() ) )
+
 	def __assertColour( self, colour1, colour2 ) :
 		for i in range( 0, 4 ):
 			self.assertEqual( "%.4f" % colour2[i], "%.4f" % colour1[i] )

src/GafferImage/ImageStats.cpp

@@ -113,9 +113,18 @@ ImageStats::ImageStats( const std::string &name )
 	addChild( new StringVectorDataPlug( "channels", Plug::In, defaultChannelsData ) );
 
 	addChild( new Box2iPlug( "area", Gaffer::Plug::In ) );
-	addChild( new Color4fPlug( "average", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ) ) );
-	addChild( new Color4fPlug( "min", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ) ) );
-	addChild( new Color4fPlug( "max", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ) ) );
+	addChild( new Color4fPlug(
+		"average", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ),
+		Imath::Color4f( -std::numeric_limits<float>::infinity() ), Imath::Color4f( std::numeric_limits<float>::infinity() )
+	) );
+	addChild(
+		new Color4fPlug( "min", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ),
+		Imath::Color4f( -std::numeric_limits<float>::infinity() ), Imath::Color4f( std::numeric_limits<float>::infinity() )
+	) );
+	addChild(
+		new Color4fPlug( "max", Gaffer::Plug::Out, Imath::Color4f( 0, 0, 0, 1 ),
+		Imath::Color4f( -std::numeric_limits<float>::infinity() ), Imath::Color4f( std::numeric_limits<float>::infinity() )
+	) );
 
 	addChild( new ObjectPlug( "__tileStats", Gaffer::Plug::Out, new IECore::V3dData() ) );
 	addChild( new ObjectPlug( "__allStats", Gaffer::Plug::Out, new IECore::V3dData() ) );
@@ -419,8 +428,8 @@ void ImageStats::compute( ValuePlug *output, const Context *context ) const
 
 		IECore::ConstFloatVectorDataPtr channelData = flattenedInPlug()->channelDataPlug()->getValue();
 
-		float min = std::numeric_limits<float>::max();
-		float max = std::numeric_limits<float>::lowest();
+		float min = std::numeric_limits<float>::infinity();
+		float max = -std::numeric_limits<float>::infinity();
 		double sum = 0.;
 
 		const std::vector<float> &channel = channelData->readable();
@@ -444,8 +453,8 @@ void ImageStats::compute( ValuePlug *output, const Context *context ) const
 			static_cast<ObjectPlug *>( output )->setValue( new IECore::V3dData( Imath::V3d( 0 ) ) );
 			return;
 		}
-		float min = std::numeric_limits<float>::max();
-		float max = std::numeric_limits<float>::lowest();
+		float min = std::numeric_limits<float>::infinity();
+		float max = -std::numeric_limits<float>::infinity();
 		double sum = 0.;
 
 		// We traverse in TopToBottom order because floating point precision means that changing