add stackblur for imgproc.

modules/imgproc/include/opencv2/imgproc.hpp

@@ -1620,6 +1620,22 @@ CV_EXPORTS_W void blur( InputArray src, OutputArray dst,
                         Size ksize, Point anchor = Point(-1,-1),
                         int borderType = BORDER_DEFAULT );
 
+/** @brief Blurs an image using the StackBlur.
+The function applies and StackBlur to an image.
+StackBlur can generate similar results as Gaussian blur, and the time does not increase as the kernel size increases.
+It creates a kind of moving stack of colors whilst scanning through the image. Thereby it just has to add one new block of color to the right side
+of the stack and remove the leftmost color. The remaining colors on the topmost layer of the stack are either added on or reduced by one,
+depending on if they are on the right or on the left side of the stack.
+Described here: http://underdestruction.com/2004/02/25/stackblur-2004.
+Stack Blur Algorithm by Mario Klingemann <mario@quasimondo.com>
+@param src input image. The number of channels can be arbitrary, but the depth should be one of
+CV_8U, CV_16U, CV_16S or CV_32F.
+@param dst output image of the same size and type as src.
+@param ksize stack-blurring kernel size. The ksize.width and ksize.height can differ but they both must be
+positive and odd.
+*/
+CV_EXPORTS_W void stackBlur(InputArray src, OutputArray dst, Size ksize);
+
 /** @brief Convolves an image with the kernel.
 
 The function applies an arbitrary linear filter to an image. In-place operation is supported. When

modules/imgproc/perf/perf_blur.cpp

@@ -253,4 +253,52 @@ PERF_TEST_P(Size_MatType, BlendLinear,
     SANITY_CHECK_NOTHING();
 }
 
+///////////// Stackblur ////////////////////////
+PERF_TEST_P(Size_MatType, stackblur3x3,
+            testing::Combine(
+                    testing::Values(sz720p, sz1080p, sz2160p),
+                    testing::Values(CV_8UC1, CV_8UC4, CV_16UC1, CV_16SC1, CV_32FC1)
+            )
+)
+{
+    Size size = get<0>(GetParam());
+    int type = get<1>(GetParam());
+    double eps = 1e-3;
+
+    eps = CV_MAT_DEPTH(type) <= CV_32S ? 1 : eps;
+
+    Mat src(size, type);
+    Mat dst(size, type);
+
+    declare.in(src, WARMUP_RNG).out(dst);
+
+    TEST_CYCLE() stackBlur(src, dst, Size(3,3));
+
+    SANITY_CHECK_NOTHING();
+}
+
+PERF_TEST_P(Size_MatType, stackblur101x101,
+            testing::Combine(
+                    testing::Values(sz720p, sz1080p, sz2160p),
+                    testing::Values(CV_8UC1, CV_8UC4, CV_16UC1, CV_16SC1, CV_32FC1)
+            )
+)
+{
+    Size size = get<0>(GetParam());
+    int type = get<1>(GetParam());
+    double eps = 1e-3;
+
+    eps = CV_MAT_DEPTH(type) <= CV_32S ? 1 : eps;
+
+    Mat src(size, type);
+    Mat dst(size, type);
+
+    declare.in(src, WARMUP_RNG).out(dst);
+
+    TEST_CYCLE() stackBlur(src, dst, Size(101,101));
+
+    SANITY_CHECK_NOTHING();
+}
+
+
 } // namespace

modules/imgproc/test/test_stackblur.cpp

@@ -0,0 +1,313 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+/*
+StackBlur - a fast almost Gaussian Blur
+Theory: http://underdestruction.com/2004/02/25/stackblur-2004
+The code has been borrowed from (https://github.com/flozz/StackBlur).
+
+Below is the original copyright
+*/
+
+/*
+Copyright (c) 2010 Mario Klingemann
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+#include "test_precomp.hpp"
+
+namespace opencv_test { namespace {
+
+template<typename T>
+void _stackblurRef(const Mat& src, Mat& dst, Size ksize)
+{
+    CV_Assert(!src.empty());
+    CV_Assert(ksize.width > 0 && ksize.height > 0 && ksize.height % 2 == 1 && ksize.width % 2 == 1);
+
+    dst.create(src.size(), src.type());
+    const int CN = src.channels();
+
+    int rowsImg = src.rows;
+    int colsImg = src.cols;
+    int wm = colsImg - 1;
+
+    int radiusW = ksize.width / 2;
+    int stackLenW = ksize.width;
+    const float mulW = 1.0f / (((float )radiusW + 1.0f) * ((float )radiusW + 1.0f));
+
+    // Horizontal direction
+    std::vector<T> stack(stackLenW * CN);
+    for (int row = 0; row < rowsImg; row++)
+    {
+        std::vector<float> sum(CN, 0);
+        std::vector<float> sumIn(CN, 0);
+        std::vector<float> sumOut(CN, 0);
+
+        const T* srcPtr = src.ptr<T>(row);
+
+        for (int i = 0; i <= radiusW; i++)
+        {
+            for (int ci = 0; ci < CN; ci++)
+            {
+                T tmp = *(srcPtr + ci);
+                stack[i * CN + ci] = tmp;
+                sum[ci] += tmp * (i + 1);
+                sumOut[ci] += tmp;
+            }
+        }
+
+        for (int i = 1; i <= radiusW; i++)
+        {
+            if (i <= wm) srcPtr += CN;
+            for(int ci = 0; ci < CN; ci++)
+            {
+                T tmp = *(srcPtr + ci);
+                stack[(i + radiusW) * CN + ci] = tmp;
+                sum[ci] += tmp * (radiusW + 1 - i);
+                sumIn[ci] += tmp;
+            }
+        }
+
+        int sp = radiusW;
+        int xp = radiusW ;
+        if (xp > wm) xp = wm;
+
+        T* dstPtr = dst.ptr<T>(row);
+        srcPtr = src.ptr<T>(row) + xp * CN;
+
+        int stackStart= 0;
+
+        for (int i = 0; i < colsImg; i++)
+        {
+            stackStart = sp + stackLenW - radiusW;
+
+            if (stackStart >= stackLenW) stackStart -= stackLenW;
+
+            for(int ci = 0; ci < CN; ci++)
+            {
+                *(dstPtr + ci) = cv::saturate_cast<T>(sum[ci] * mulW);
+                sum[ci] -= sumOut[ci];
+                sumOut[ci] -= stack[stackStart*CN + ci];
+            }
+
+            const T* srcNew = srcPtr;
+
+            if(xp < wm)
+                srcNew += CN;
+
+            for (int ci = 0; ci < CN; ci++)
+            {
+                stack[stackStart * CN + ci] = *(srcNew + ci);
+                sumIn[ci] += *(srcNew + ci);
+                sum[ci] += sumIn[ci];
+            }
+
+            int sp1 = sp + 1;
+            sp1 &= -(sp1 < stackLenW);
+
+            for(int ci = 0; ci < CN; ci++)
+            {
+                T tmp = stack[sp1*CN + ci];
+                sumOut[ci] += tmp;
+                sumIn[ci] -= tmp;
+            }
+
+            dstPtr += CN;
+
+            if (xp < wm)
+            {
+                xp++;
+                srcPtr += CN;
+            }
+
+            ++sp;
+            if (sp >= stackLenW) sp = 0;
+        }
+    }
+
+    // Vertical direction
+    int hm = rowsImg - 1;
+    int widthElem = colsImg * CN;
+    int radiusH = ksize.height / 2;
+    int stackLenH = ksize.height;
+    const float mulH = 1.0f / (((float )radiusH + 1.0f) * ((float )radiusH + 1.0f));
+
+    stack.resize(stackLenH, 0);
+    for (int col = 0; col < widthElem; col++)
+    {
+        const T* srcPtr =dst.ptr<T>() + col;
+        float sum0 = 0;
+        float sumIn0 = 0;
+        float sumOut0 = 0;
+
+        for (int i = 0; i <= radiusH; i++)
+        {
+            T tmp = (T)(*srcPtr);
+            stack[i] = tmp;
+            sum0 += tmp * (i + 1);
+            sumOut0 += tmp;
+        }
+
+        for (int i = 1; i <= radiusH; i++)
+        {
+            if (i <= hm) srcPtr += widthElem;
+            T tmp = (T)(*srcPtr);
+            stack[i + radiusH] = tmp;
+            sum0 += tmp * (radiusH - i + 1);
+            sumIn0 += tmp;
+        }
+
+        int sp = radiusH;
+        int yp = radiusH;
+
+        if (yp > hm) yp = hm;
+
+        T* dstPtr = dst.ptr<T>() + col;
+        srcPtr = dst.ptr<T>(yp) + col;
+
+        const T* srcNew;
+
+        int stackStart = 0;
+
+        for (int i = 0; i < rowsImg; i++)
+        {
+            stackStart = sp + stackLenH - radiusH;
+            if (stackStart >= stackLenH) stackStart -= stackLenH;
+
+            *(dstPtr) = saturate_cast<T>(sum0 * mulH);
+            sum0 -= sumOut0;
+            sumOut0 -= stack[stackStart];
+            srcNew = srcPtr;
+
+            if (yp < hm)
+                srcNew += widthElem;
+
+            stack[stackStart] = *(srcNew);
+            sumIn0 += *(srcNew);
+            sum0 += sumIn0;
+
+            int sp1 = sp + 1;
+            sp1 &= -(sp1 < stackLenH);
+
+            sumOut0 += stack[sp1];
+            sumIn0 -= stack[sp1];
+
+            dstPtr += widthElem;
+
+            if (yp < hm)
+            {
+                yp++;
+                srcPtr += widthElem;
+            }
+
+            ++sp;
+            if (sp >= stackLenH) sp = 0;
+        }
+    }
+}
+
+void stackBlurRef(const Mat& img, Mat& dst, Size ksize)
+{
+    if(img.depth() == CV_8U)
+        _stackblurRef<uchar>(img, dst, ksize);
+    else if (img.depth() == CV_16S)
+        _stackblurRef<short>(img, dst, ksize);
+    else if (img.depth() == CV_16U)
+        _stackblurRef<ushort>(img, dst, ksize);
+    else if (img.depth() == CV_32F)
+        _stackblurRef<float>(img, dst, ksize);
+    else
+        CV_Error_( CV_StsNotImplemented,
+                   ("Unsupported Mat type in stackBlurRef, "
+                    "the supported formats are: CV_8U, CV_16U, CV_16S and CV_32F."));
+}
+
+std::vector<Size> kernelSizeVec = {
+                Size(3, 3),
+                Size(5, 5),
+                Size(101, 101),
+                Size(3, 9)
+        };
+
+typedef testing::TestWithParam<tuple<int, int, int> > StackBlur;
+
+TEST_P (StackBlur, regression)
+{
+    Mat img_ = imread(findDataFile("shared/fruits.png"), 1);
+    const int cn = get<0>(GetParam());
+    const int kIndex = get<1>(GetParam());
+    const int dtype = get<2>(GetParam());
+
+    Size ksize = kernelSizeVec[kIndex];
+
+    Mat img, dstRef, dst;
+    convert(img_, img, dtype);
+
+    vector<Mat> channels;
+    split(img, channels);
+    channels.push_back(channels[0]); // channels size is 4.
+
+    Mat imgCn;
+    if (cn == 1)
+        imgCn = channels[0];
+    else if (cn == 4)
+        merge(channels, imgCn);
+    else
+        imgCn = img;
+
+    stackBlurRef(imgCn, dstRef, ksize);
+    stackBlur(imgCn, dst, ksize);
+    EXPECT_LE(cvtest::norm(dstRef, dst, NORM_INF), 2.);
+}
+
+INSTANTIATE_TEST_CASE_P(Imgproc, StackBlur,
+                        testing::Combine(
+                                testing::Values(1, 3, 4),
+                                testing::Values(0, 1, 2, 3),
+                                testing::Values(CV_8U, CV_16S, CV_16U, CV_32F)
+                        )
+);
+
+typedef testing::TestWithParam<tuple<int> > StackBlur_GaussianBlur;
+
+// StackBlur should produce similar results as GaussianBlur output.
+TEST_P(StackBlur_GaussianBlur, compare)
+{
+    Mat img_ = imread(findDataFile("shared/fruits.png"), 1);
+    const int dtype = get<0>(GetParam());
+
+    Size ksize(3, 3);
+    Mat img, dstS, dstG;
+    convert(img_, img, dtype);
+
+    stackBlur(img, dstS, ksize);
+    GaussianBlur(img,  dstG, ksize, 0);
+
+    EXPECT_LE(cvtest::norm(dstS, dstG, NORM_INF), 13.);
+}
+
+INSTANTIATE_TEST_CASE_P(Imgproc, StackBlur_GaussianBlur, testing::Values(CV_8U, CV_16S, CV_16U, CV_32F));
+}
+}