From b933b67d8d063f3e3d4f0d35cd025c2923e96035 Mon Sep 17 00:00:00 2001
From: Sebastien Harasse <sebastien.harasse@c-s.fr>
Date: Tue, 24 Apr 2012 18:01:37 +0200
Subject: [PATCH] ENH: Mean shift. VariableSizeVector's element-wise operators
caused performance hit -> Changed to loops over the vector dimension.
---
.../BasicFilters/otbMeanShiftImageFilter2.txx | 33 +++++++++++++------
1 file changed, 23 insertions(+), 10 deletions(-)
diff --git a/Code/BasicFilters/otbMeanShiftImageFilter2.txx b/Code/BasicFilters/otbMeanShiftImageFilter2.txx
index 729c0b8d0c..d155a2e78c 100644
--- a/Code/BasicFilters/otbMeanShiftImageFilter2.txx
+++ b/Code/BasicFilters/otbMeanShiftImageFilter2.txx
@@ -293,6 +293,7 @@ void
MeanShiftImageFilter2<TInputImage, TOutputImage, TKernel, TNorm, TOutputMetricImage, TOutputIterationImage>
::CalculateMeanShiftVector(typename RealVectorImageType::Pointer jointImage, RealVector jointPixel, const OutputRegionType& outputRegion, RealVector & meanShiftVector)
{
+ unsigned int jointDimension = ImageDimension + m_NumberOfComponentsPerPixel;
RealVector jointNeighbor;
RealType weightSum = 0;
@@ -326,23 +327,27 @@ MeanShiftImageFilter2<TInputImage, TOutputImage, TKernel, TNorm, TOutputMetricIm
it.GoToBegin();
while(!it.IsAtEnd())
{
- RealVector diff;
RealType norm2;
RealType weight;
jointNeighbor = it.Get();
- // Calculate the squared norm of the difference
- diff = jointNeighbor - jointPixel;
-
// Compute the squared norm of the difference
// This is the L2 norm, TODO: replace by the templated norm
- norm2 = diff.GetSquaredNorm();
+ norm2 = 0;
+ for(unsigned int comp = 0; comp < jointDimension; comp++)
+ {
+ RealType d;
+ d = jointNeighbor[comp] - jointPixel[comp];
+ norm2 += d*d;
+ }
+
// Compute pixel weight from kernel
// TODO : replace by the templated kernel
weight = (norm2 <= 1.0)? 1.0 : 0.0;
- /*
+
+/*
// The following code is an alternative way to compute norm2 and weight
// It separates the norms of spatial and range elements
RealType spatialNorm2;
@@ -350,7 +355,9 @@ MeanShiftImageFilter2<TInputImage, TOutputImage, TKernel, TNorm, TOutputMetricIm
spatialNorm2 = 0;
for (unsigned int comp = 0; comp < ImageDimension; comp++)
{
- spatialNorm2 += diff[comp] * diff[comp];
+ RealType d;
+ d = jointNeighbor[comp] - jointPixel[comp];
+ spatialNorm2 += d*d;
}
if(spatialNorm2 >= 1.0)
@@ -362,18 +369,24 @@ MeanShiftImageFilter2<TInputImage, TOutputImage, TKernel, TNorm, TOutputMetricIm
rangeNorm2 = 0;
for (unsigned int comp = 0; comp < m_NumberOfComponentsPerPixel; comp++)
{
- rangeNorm2 += diff[ImageDimension + comp] * diff[ImageDimension + comp];
+ RealType d;
+ d = jointNeighbor[ImageDimension + comp] - jointPixel[ImageDimension + comp];
+ rangeNorm2 += d*d;
}
weight = (rangeNorm2 <= 1.0)? 1.0 : 0.0;
}
- */
+*/
// Update sum of weights
weightSum += weight;
// Update mean shift vector
- meanShiftVector += weight * jointNeighbor;
+ for(unsigned int comp = 0; comp < jointDimension; comp++)
+ {
+ meanShiftVector[comp] += weight * jointNeighbor[comp];
+ }
+
++it;
}
--
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