alpha matting code

Author: sunitanyk

modules/README.md

@@ -10,6 +10,8 @@ $ cmake -D OPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules -D BUILD_opencv_<r
 
 - **aruco**: ArUco and ChArUco Markers -- Augmented reality ArUco marker and "ChARUco" markers where ArUco markers embedded inside the white areas of the checker board.
 
+- **alphamat**: Computer Vision based Alpha Matting -- Given an input image and a trimap, generate an alpha matte.
+
 - **bgsegm**: Background segmentation algorithm combining statistical background image estimation and per-pixel Bayesian segmentation.
 
 - **bioinspired**: Biological Vision -- Biologically inspired vision model: minimize noise and luminance variance, transient event segmentation, high dynamic range tone mapping methods.

modules/alphamat/CMakeLists.txt

@@ -0,0 +1,14 @@
+if(NOT HAVE_EIGEN)
+  set(DISABLE_MSG "Module opencv_alphamat disabled because the following dependencies are not found:")
+  set(DISABLE_MSG "${DISABLE_MSG} Eigen")
+  message(STATUS ${DISABLE_MSG})
+  ocv_module_disable(alphamat)
+endif()
+
+cmake_minimum_required (VERSION 3.0)
+project (myproject)
+set (CMAKE_CXX_STANDARD 11)
+
+ocv_define_module(alphamat opencv_core
+    opencv_imgproc
+)

modules/alphamat/README.md

@@ -0,0 +1,23 @@
+# Computer Vision based Alpha Matting
+
+This project was part of the Google Summer of Code 2019.
+
+####Student: Muskaan Kularia
+####Mentor: Sunita Nayak
+***
+Alphamatting is the problem of extracting the foreground from an image. Given the input of an image and its corresponding trimap, we try to extract the foreground from the background.
+
+This project is implementation of "[[Designing Effective Inter-Pixel Information Flow for Natural Image Matting](http://people.inf.ethz.ch/aksoyy/ifm/)]" by Yağız Aksoy, Tunç Ozan Aydın and Marc Pollefeys[1]. It required implementation of parts of other papers [2,3,4].
+
+
+## References
+
+[1] Yagiz Aksoy, Tunc Ozan Aydin, Marc Pollefeys, "[Designing Effective Inter-Pixel Information Flow for Natural Image Matting](http://people.inf.ethz.ch/aksoyy/ifm/)", CVPR, 2017.
+
+[2] Roweis, Sam T., and Lawrence K. Saul. "[Nonlinear dimensionality reduction by locally linear embedding](https://science.sciencemag.org/content/290/5500/2323)" Science 290.5500 (2000): 2323-2326.
+
+[3] Anat Levin, Dani Lischinski, Yair Weiss, "[A Closed Form Solution to Natural Image Matting](https://www.researchgate.net/publication/5764820_A_Closed-Form_Solution_to_Natural_Image_Matting)", IEEE TPAMI, 2008.
+
+[4] Qifeng Chen, Dingzeyu Li, Chi-Keung Tang, "[KNN Matting](http://dingzeyu.li/files/knn-matting-tpami.pdf)", IEEE TPAMI, 2013.
+
+[5] Yagiz Aksoy, "[Affinity Based Matting Toolbox](https://github.com/yaksoy/AffinityBasedMattingToolbox)".

modules/alphamat/doc/alphamat.bib

@@ -0,0 +1,26 @@
+@inproceedings{aksoy2017designing,
+  title={Designing effective inter-pixel information flow for natural image matting},
+  author={Aksoy, Yagiz and Ozan Aydin, Tunc and Pollefeys, Marc},
+  booktitle={Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition},
+  pages={29--37},
+  year={2017}
+}
+
+@article{roweis2000nonlinear,
+  title={Nonlinear dimensionality reduction by locally linear embedding},
+  author={Roweis, Sam T and Saul, Lawrence K},
+  journal={science},
+  volume={290},
+  number={5500},
+  pages={2323--2326},
+  year={2000},
+  publisher={American Association for the Advancement of Science}
+}
+
+@inproceedings{shahrian2013improving,
+  title={Improving image matting using comprehensive sampling sets},
+  author={Shahrian, Ehsan and Rajan, Deepu and Price, Brian and Cohen, Scott},
+  booktitle={Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition},
+  pages={636--643},
+  year={2013}
+}

modules/alphamat/include/opencv2/infoflow.hpp

@@ -0,0 +1,21 @@
+// 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.
+
+/** Information Flow algorithm implementaton for alphamatting*/
+
+#ifndef _OPENCV_ALPHAMAT_INFOFLOW_HPP_
+#define _OPENCV_ALPHAMAT_INFOFLOW_HPP_
+
+#include <Eigen/Sparse>
+using namespace Eigen;
+
+namespace cv{ namespace alphamat{
+
+    void solve(SparseMatrix<double> Wcm,SparseMatrix<double> Wuu,SparseMatrix<double> Wl,SparseMatrix<double> Dcm,
+            SparseMatrix<double> Duu,SparseMatrix<double> Dl, SparseMatrix<double> T, Mat& wf, Mat& alpha);
+
+    CV_EXPORTS_W void infoFlow(Mat& image, Mat& tmap, Mat& result);
+
+}}
+#endif

modules/alphamat/samples/information_flow_matting.cpp

@@ -0,0 +1,81 @@
+// 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.
+
+#include <iostream>
+#include "opencv2/highgui.hpp"
+#include <opencv2/core/base.hpp>
+#include <opencv2/core/utility.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/infoflow.hpp>
+
+using namespace std;
+using namespace cv;
+using namespace cv::alphamat;
+
+const char* keys =
+{
+    "{img || input image name}"
+    "{tri || input trimap image name}"
+    "{out || output image name}"
+};
+
+int main(int argc, char *argv[])
+{
+    bool show_help = (argc == 1);
+    show_help = show_help || (argc == 2 && string(argv[1]) == "--help");
+    show_help = show_help || (argc == 2 && string(argv[1]) == "-h");
+
+    if (show_help)
+    {
+        printf("\nThis sample demonstrates Information Flow alpha matting\n"
+               "Call:\n"
+               "    %s -img=<string> -tri=<string> [-out=<string>]\n\n", argv[0]);
+        return 0;
+    }
+
+    CommandLineParser parser(argc, argv, keys);
+    if (!parser.check())
+    {
+        parser.printErrors();
+        return -1;
+    }
+
+    string img_path = parser.get<std::string>("img");
+    string trimap_path = parser.get<std::string>("tri");
+    string result_path = parser.get<std::string>("out");
+
+    Mat image, tmap;
+
+    image = imread(img_path, IMREAD_COLOR);   // Read the input image file
+    if (image.empty())
+    {
+        printf("Cannot read image file: %s\n", img_path.c_str());
+        return -1;
+    }
+
+    tmap = imread(trimap_path, IMREAD_GRAYSCALE);
+    if (tmap.empty())
+    {
+        printf("Cannot read trimap file: %s\n", trimap_path.c_str());
+        return -1;
+    }
+
+    Mat result;
+    infoFlow(image, tmap, result);
+
+    if (result_path.empty())
+    {
+        namedWindow("result alpha matte", WINDOW_NORMAL);
+        imshow("result alpha matte", result);
+        waitKey(0);
+    }
+    else
+    {
+        imwrite(result_path, result);
+    }
+
+    imshow("Result Matte", result);
+    return 0;
+
+}