CPU implementation of CLAHE

modules/imgproc/include/opencv2/imgproc/imgproc.hpp

@@ -759,6 +759,21 @@ CV_EXPORTS double compareHist( const SparseMat& H1, const SparseMat& H2, int met
 //! normalizes the grayscale image brightness and contrast by normalizing its histogram
 CV_EXPORTS_W void equalizeHist( InputArray src, OutputArray dst );
 
+class CV_EXPORTS CLAHE : public Algorithm
+{
+public:
+    virtual void apply(InputArray src, OutputArray dst) = 0;
+
+    virtual void setClipLimit(double clipLimit) = 0;
+    virtual double getClipLimit() const = 0;
+
+    virtual void setTilesGridSize(Size tileGridSize) = 0;
+    virtual Size getTilesGridSize() const = 0;
+
+    virtual void collectGarbage() = 0;
+};
+CV_EXPORTS Ptr<CLAHE> createCLAHE(double clipLimit = 40.0, Size tileGridSize = Size(8, 8));
+
 CV_EXPORTS float EMD( InputArray signature1, InputArray signature2,
                       int distType, InputArray cost=noArray(),
                       float* lowerBound=0, OutputArray flow=noArray() );

modules/imgproc/perf/perf_histogram.cpp

@@ -115,3 +115,25 @@ PERF_TEST_P(MatSize, equalizeHist,
 
     SANITY_CHECK(destination);
 }
+
+typedef tr1::tuple<Size, double> Sz_ClipLimit_t;
+typedef TestBaseWithParam<Sz_ClipLimit_t> Sz_ClipLimit;
+
+PERF_TEST_P(Sz_ClipLimit, CLAHE,
+            testing::Combine(testing::Values(::perf::szVGA, ::perf::sz720p, ::perf::sz1080p),
+                             testing::Values(0.0, 40.0))
+            )
+{
+    const Size size = get<0>(GetParam());
+    const double clipLimit = get<1>(GetParam());
+
+    Mat src(size, CV_8UC1);
+    declare.in(src, WARMUP_RNG);
+
+    Ptr<CLAHE> clahe = createCLAHE(clipLimit);
+    Mat dst;
+
+    TEST_CYCLE() clahe->apply(src, dst);
+
+    SANITY_CHECK(dst);
+}