added optimized anisotropic diffusion filter (rewrite of…

added optimized anisotropic diffusion filter (rewrite of https://github.com/opencv/opencv/pull/8362)

modules/ximgproc/include/opencv2/ximgproc.hpp

@@ -122,6 +122,27 @@ The function transforms a binary blob image into a skeletized form using the tec
  */
 CV_EXPORTS_W void thinning( InputArray src, OutputArray dst, int thinningType = THINNING_ZHANGSUEN);
 
+/** @brief Performs anisotropic diffusian on an image.
+ 
+ The function applies Perona-Malik anisotropic diffusion to an image. This is the solution to the partial differential equation:
+ 
+ \f[{\frac  {\partial I}{\partial t}}={\mathrm  {div}}\left(c(x,y,t)\nabla I\right)=\nabla c\cdot \nabla I+c(x,y,t)\Delta I\f]
+ 
+ Suggested functions for c(x,y,t) are:
+ 
+ \f[c\left(\|\nabla I\|\right)=e^{{-\left(\|\nabla I\|/K\right)^{2}}}\f]
+ 
+ or
+ 
+ \f[ c\left(\|\nabla I\|\right)={\frac {1}{1+\left({\frac  {\|\nabla I\|}{K}}\right)^{2}}} \f]
+ 
+ @param src Grayscale Source image.
+ @param dst Destination image of the same size and the same number of channels as src .
+ @param alpha The amount of time to step forward by on each iteration (normally, it's between 0 and 1).
+ @param K sensitivity to the edges
+ @param niters The number of iterations
+*/
+CV_EXPORTS_W void anisotropicDiffusion(InputArray src, OutputArray dst, float alpha, float K, int niters );
 
 //! @}
 

modules/ximgproc/samples/filterdemo.cpp

+/*M///////////////////////////////////////////////////////////////////////////////////////
+//
+//  IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
+//
+//  By downloading, copying, installing or using the software you agree to this license.
+//  If you do not agree to this license, do not download, install,
+//  copy or use the software.
+//
+//
+//                           License Agreement
+//                For Open Source Computer Vision Library
+//
+// Copyright (C) 2017, Intel Corporation, all rights reserved.
+// Third party copyrights are property of their respective owners.
+//
+// Redistribution and use in source and binary forms, with or without modification,
+// are permitted provided that the following conditions are met:
+//
+//   * Redistribution's of source code must retain the above copyright notice,
+//     this list of conditions and the following disclaimer.
+//
+//   * Redistribution's in binary form must reproduce the above copyright notice,
+//     this list of conditions and the following disclaimer in the documentation
+//     and/or other materials provided with the distribution.
+//
+//   * The name of the copyright holders may not be used to endorse or promote products
+//     derived from this software without specific prior written permission.
+//
+// This software is provided by the copyright holders and contributors "as is" and
+// any express or implied warranties, including, but not limited to, the implied
+// warranties of merchantability and fitness for a particular purpose are disclaimed.
+// In no event shall the Intel Corporation or contributors be liable for any direct,
+// indirect, incidental, special, exemplary, or consequential damages
+// (including, but not limited to, procurement of substitute goods or services;
+// loss of use, data, or profits; or business interruption) however caused
+// and on any theory of liability, whether in contract, strict liability,
+// or tort (including negligence or otherwise) arising in any way out of
+// the use of this software, even if advised of the possibility of such damage.
+//
+//M*/
+
+#include "opencv2/core/utility.hpp"
+#include "opencv2/imgproc.hpp"
+#include "opencv2/imgcodecs.hpp"
+#include "opencv2/highgui.hpp"
+#include "opencv2/ximgproc.hpp"
+
+#include <stdio.h>
+
+using namespace cv;
+using namespace std;
+
+int main( int argc, const char** argv)
+{
+    float alpha = 1.0f;
+    float sigma = 0.02f;
+    int rows0 = 480;
+    int niters = 10;
+    Mat frame, src, dst;
+
+    const char* window_name = "Anisodiff : Exponential Flux";
+
+    VideoCapture cap;
+    if( argc > 1 )
+        cap.open(argv[1]);
+    else
+        cap.open(0);
+
+    if (!cap.isOpened())
+    {
+        printf("Cannot initialize video capturing\n");
+        return 0;
+    }
+
+    // Create a window
+    namedWindow(window_name, 1);
+
+    // create a toolbar
+    createTrackbar("No. of time steps", window_name, &niters, 30, 0);
+
+    for(;;)
+    {
+        cap >> frame;
+        if( frame.empty() )
+            break;
+
+        if( frame.rows <= rows0 )
+            src = frame;
+        else
+            resize(frame, src, Size(cvRound(480.*frame.cols/frame.rows), 480));
+
+        float t = (float)getTickCount();
+        ximgproc::anisotropicDiffusion(src, dst, alpha, sigma, niters);
+        t = (float)getTickCount() - t;
+        printf("time: %.1fms\n", t*1000./getTickFrequency());
+        imshow(window_name, dst);
+
+        // Wait for a key stroke; the same function arranges events processing
+        char c = (char)waitKey(30);
+        if(c >= 0)
+            break;
+    }
+
+    return 0;
+}

modules/ximgproc/src/opencl/anisodiff.cl

+__kernel void anisodiff(__global const uchar * srcptr, int srcstep, int srcoffset,
+                        __global uchar * dstptr, int dststep, int dstoffset,
+                        int rows, int cols, __constant float* exptab, float alpha)
+{
+    int x = get_global_id(0);
+    int y = get_global_id(1);
+
+    if( x < cols && y < rows )
+    {
+        int yofs = y*dststep + x*3;
+        int xofs = y*srcstep + x*3;
+        float4 s = 0.f;
+
+        float4 c = (float4)(srcptr[xofs], srcptr[xofs+1], srcptr[xofs+2], 0.f);
+        float4 delta, adelta;
+        float w;
+
+        #define UPDATE_SUM(xofs1) \
+            delta = (float4)(srcptr[xofs + xofs1], srcptr[xofs + xofs1 + 1], srcptr[xofs + xofs1 + 2], 0.f) - c; \
+            adelta = fabs(delta); \
+            w = exptab[convert_int(adelta.x + adelta.y + adelta.z)]; \
+            s += delta*w
+
+        UPDATE_SUM(3);
+        UPDATE_SUM(-3);
+        UPDATE_SUM(-srcstep-3);
+        UPDATE_SUM(-srcstep);
+        UPDATE_SUM(-srcstep+3);
+        UPDATE_SUM(srcstep-3);
+        UPDATE_SUM(srcstep);
+        UPDATE_SUM(srcstep+3);
+
+        s = s*alpha + c;
+        uchar4 d = convert_uchar4_sat(convert_int4_rte(s));
+        dstptr[yofs] = d.x;
+        dstptr[yofs+1] = d.y;
+        dstptr[yofs+2] = d.z;
+    }
+}

modules/ximgproc/test/test_anisodiff.cpp

+#include "test_precomp.hpp"
+
+using namespace cv;
+using namespace std;
+
+TEST(ximgproc_AnisotropicDiffusion, regression)
+{
+    string folder = string(cvtest::TS::ptr()->get_data_path()) + "shared/";
+    string original_path = folder + "fruits.png";
+
+    Mat original = imread(original_path, IMREAD_COLOR);
+
+    ASSERT_FALSE(original.empty()) << "Could not load input image " << original_path;
+    ASSERT_EQ(3, original.channels()) << "Load color input image " << original_path;
+
+    Mat result;
+    float alpha = 1.0f;
+    float K = 0.02f;
+    int niters = 10;
+    ximgproc::anisotropicDiffusion(original, result, alpha, K, niters);
+
+    double adiff_psnr = cvtest::PSNR(original, result);
+    //printf("psnr=%.2f\n", adiff_psnr);
+    ASSERT_GT(adiff_psnr, 25.0);
+}