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/anisodiff.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*/
+
+/* the reference code has been contributed by Chris Sav */
+
+#include "precomp.hpp"
+#include "opencv2/core/hal/intrin.hpp"
+#include "opencl_kernels_ximgproc.hpp"
+
+namespace cv {
+namespace ximgproc {
+
+#if CV_SIMD128
+inline void v_expand_s(const v_uint8x16& a, v_int16x8& b, v_int16x8& c)
+{
+    v_uint16x8 t0, t1;
+    v_expand(a, t0, t1);
+    b = v_reinterpret_as_s16(t0);
+    c = v_reinterpret_as_s16(t1);
+}
+
+inline void v_expand_f32(const v_int16x8& a, v_float32x4& b, v_float32x4& c)
+{
+    v_int32x4 t0, t1;
+    v_expand(a, t0, t1);
+    b = v_cvt_f32(t0);
+    c = v_cvt_f32(t1);
+}
+
+inline v_uint8x16 v_finalize_pix_ch(const v_int16x8& c0, const v_int16x8& c1,
+                                    const v_float32x4& s0, const v_float32x4& s1,
+                                    const v_float32x4& s2, const v_float32x4& s3,
+                                    const v_float32x4& alpha)
+{
+    v_float32x4 f0, f1, f2, f3;
+    v_expand_f32(c0, f0, f1);
+    v_expand_f32(c1, f2, f3);
+
+    v_int16x8 d0 = v_pack(v_round(s0*alpha + f0), v_round(s1*alpha + f1));
+    v_int16x8 d1 = v_pack(v_round(s2*alpha + f2), v_round(s3*alpha + f3));
+
+    return v_pack_u(d0, d1);
+}
+#endif
+
+class ADBody : public ParallelLoopBody
+{
+public:
+    ADBody(const Mat* src_, Mat* dst_, const float* exptab, float alpha)
+    {
+        src = src_;
+        dst = dst_;
+        exptab_ = exptab;
+        alpha_ = alpha;
+    }
+
+    void operator()(const Range& range) const
+    {
+        const int cn = 3;
+        int cols = src->cols;
+        int step = (int)src->step;
+        int tab[] = { -cn, cn, -step-cn, -step, -step+cn, step-cn, step, step+cn };
+        float alpha = alpha_;
+        const float* exptab = exptab_;
+
+        for( int i = range.start; i < range.end; i++ )
+        {
+            const uchar* psrc0 = src->ptr<uchar>(i);
+            uchar* pdst = dst->ptr<uchar>(i);
+            int j = 0;
+
+#if CV_SIMD128
+            v_float32x4 v_alpha = v_setall_f32(alpha);
+            for( ; j <= cols - 16; j += 16 )
+            {
+                v_uint8x16 c0, c1, c2;
+                v_load_deinterleave(psrc0 + j*3, c0, c1, c2);
+                v_int16x8 c00, c01, c10, c11, c20, c21;
+
+                v_expand_s(c0, c00, c01);
+                v_expand_s(c1, c10, c11);
+                v_expand_s(c2, c20, c21);
+
+                v_float32x4 s00 = v_setzero_f32(), s01 = s00, s02 = s00, s03 = s00;
+                v_float32x4 s10 = v_setzero_f32(), s11 = s00, s12 = s00, s13 = s00;
+                v_float32x4 s20 = v_setzero_f32(), s21 = s00, s22 = s00, s23 = s00;
+                v_float32x4 fd0, fd1, fd2, fd3;
+
+                for( int k = 0; k < 8; k++ )
+                {
+                    const uchar* psrc1 = psrc0 + j*3 + tab[k];
+                    v_uint8x16 p0, p1, p2;
+                    v_int16x8 p00, p01, p10, p11, p20, p21;
+                    v_load_deinterleave(psrc1, p0, p1, p2);
+
+                    v_expand_s(p0, p00, p01);
+                    v_expand_s(p1, p10, p11);
+                    v_expand_s(p2, p20, p21);
+
+                    v_int16x8 d00 = p00 - c00, d01 = p01 - c01;
+                    v_int16x8 d10 = p10 - c10, d11 = p11 - c11;
+                    v_int16x8 d20 = p20 - c20, d21 = p21 - c21;
+
+                    v_uint16x8 n0 = v_abs(d00) + v_abs(d10) + v_abs(d20);
+                    v_uint16x8 n1 = v_abs(d01) + v_abs(d11) + v_abs(d21);
+
+                    ushort CV_DECL_ALIGNED(16) nbuf[16];
+                    v_store(nbuf, n0);
+                    v_store(nbuf + 8, n1);
+
+                    v_float32x4 w0(exptab[nbuf[0]], exptab[nbuf[1]], exptab[nbuf[2]], exptab[nbuf[3]]);
+                    v_float32x4 w1(exptab[nbuf[4]], exptab[nbuf[5]], exptab[nbuf[6]], exptab[nbuf[7]]);
+                    v_float32x4 w2(exptab[nbuf[8]], exptab[nbuf[9]], exptab[nbuf[10]], exptab[nbuf[11]]);
+                    v_float32x4 w3(exptab[nbuf[12]], exptab[nbuf[13]], exptab[nbuf[14]], exptab[nbuf[15]]);
+
+                    v_expand_f32(d00, fd0, fd1);
+                    v_expand_f32(d01, fd2, fd3);
+                    s00 += fd0*w0; s01 += fd1*w1; s02 += fd2*w2; s03 += fd3*w3;
+                    v_expand_f32(d10, fd0, fd1);
+                    v_expand_f32(d11, fd2, fd3);
+                    s10 += fd0*w0; s11 += fd1*w1; s12 += fd2*w2; s13 += fd3*w3;
+                    v_expand_f32(d20, fd0, fd1);
+                    v_expand_f32(d21, fd2, fd3);
+                    s20 += fd0*w0; s21 += fd1*w1; s22 += fd2*w2; s23 += fd3*w3;
+                }
+
+                c0 = v_finalize_pix_ch(c00, c01, s00, s01, s02, s03, v_alpha);
+                c1 = v_finalize_pix_ch(c10, c11, s10, s11, s12, s13, v_alpha);
+                c2 = v_finalize_pix_ch(c20, c21, s20, s21, s22, s23, v_alpha);
+                v_store_interleave(pdst + j*3, c0, c1, c2);
+            }
+            j *= 3;
+#endif
+            
+            for( ; j < cols*cn; j += cn )
+            {
+                int c0  = psrc0[j], c1 = psrc0[j+1], c2 = psrc0[j+2];
+                float s0 = 0.f, s1 = 0.f, s2 = 0.f;
+                for( int k = 0; k < 8; k++ )
+                {
+                    const uchar* psrc1 = psrc0 + j + tab[k];
+                    int delta0 = psrc1[0] - c0;
+                    int delta1 = psrc1[1] - c1;
+                    int delta2 = psrc1[2] - c2;
+                    int nabla = std::abs(delta0) + std::abs(delta1) + std::abs(delta2);
+                    float w = exptab[nabla];
+                    s0 += delta0*w;
+                    s1 += delta1*w;
+                    s2 += delta2*w;
+                }
+                pdst[j] = saturate_cast<uchar>(c0 + alpha*s0);
+                pdst[j+1] = saturate_cast<uchar>(c1 + alpha*s1);
+                pdst[j+2] = saturate_cast<uchar>(c2 + alpha*s2);
+            }
+        }
+    }
+    
+    const Mat* src;
+    Mat* dst;
+    const float* exptab_;
+    float alpha_;
+};
+
+#ifdef HAVE_OPENCL
+static bool ocl_anisotropicDiffusion(InputArray src_, OutputArray dst_,
+                                     float alpha, int niters,
+                                     const std::vector<float>& exptab)
+{
+    UMat src0 = src_.getUMat(), dst0 = dst_.getUMat();
+    int type = src0.type();
+    int rows = src0.rows, cols = src0.cols;
+
+    ocl::Kernel k("anisodiff", ocl::ximgproc::anisodiff_oclsrc, "");
+    if (k.empty())
+        return false;
+
+    UMat temp0x(rows + 2, cols + 2, type);
+    UMat temp1x(rows + 2, cols + 2, type);
+    UMat temp0(temp0x, Rect(1, 1, cols, rows));
+    UMat temp1(temp1x, Rect(1, 1, cols, rows));
+
+    int tabsz = (int)exptab.size();
+    UMat uexptab = Mat(1, tabsz, CV_32F, (void*)&exptab[0]).getUMat(ACCESS_READ);
+
+    for (int t = 0; t < niters; t++)
+    {
+        UMat src = temp0, dst = t == niters-1 ? dst0 : temp1;
+        copyMakeBorder(t == 0 ? src0 : src, temp0x, 1, 1, 1, 1, BORDER_REPLICATE);
+
+        k.args(ocl::KernelArg::ReadOnlyNoSize(src), ocl::KernelArg::WriteOnly(dst),
+               ocl::KernelArg::PtrReadOnly(uexptab), alpha);
+
+        size_t globalsize[] = { cols, rows };
+        if(!k.run(2, globalsize, NULL, true))
+            return false;
+
+        std::swap(temp0, temp1);
+        std::swap(temp0x, temp1x);
+    }
+    return true;
+}
+#endif
+
+void anisotropicDiffusion(InputArray src_, OutputArray dst_, float alpha, float K, int niters )
+{
+    if( niters == 0 )
+    {
+        src_.copyTo(dst_);
+        return;
+    }
+
+    int type = src_.type();
+    CV_Assert(src_.dims() == 2 && type == CV_8UC3);
+    CV_Assert(K != 0);
+    CV_Assert(alpha > 0);
+    CV_Assert(niters >= 0);
+
+    const int cn = 3;
+    float sigma = K * cn * 255.f;
+    float isigma2 = 1 / (sigma * sigma);
+    std::vector<float> exptab_(255*3);
+    float* exptab = &exptab_[0];
+
+    for( int k = 0; k < 255*3; k++ )
+        exptab[k] = std::exp(-k*k*isigma2);
+
+    dst_.create(src_.size(), type);
+
+    CV_OCL_RUN(dst_.isUMat(),
+               ocl_anisotropicDiffusion(src_, dst_, alpha, niters, exptab_));
+
+    Mat src0 = src_.getMat();
+    int rows = src0.rows, cols = src0.cols;
+
+    Mat dst0 = dst_.getMat();
+    Mat temp0x(rows + 2, cols + 2, type);
+    Mat temp1x(rows + 2, cols + 2, type);
+    Mat temp0(temp0x, Rect(1, 1, cols, rows));
+    Mat temp1(temp1x, Rect(1, 1, cols, rows));
+
+    for (int t = 0; t < niters; t++)
+    {
+        Mat src = temp0, dst = t == niters-1 ? dst0 : temp1;
+        copyMakeBorder(t == 0 ? src0 : src, temp0x, 1, 1, 1, 1, BORDER_REPLICATE);
+
+        ADBody body(&src, &dst, exptab, alpha);
+        parallel_for_(Range(0, rows), body, 8);
+        
+        std::swap(temp0, temp1);
+        std::swap(temp0x, temp1x);
+    }
+}
+
+}
+}
+

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);
+}