added func to different colors generation

modules/contrib/include/opencv2/contrib/contrib.hpp

@@ -613,6 +613,16 @@ namespace cv
 			static std::vector<std::string> GetListFilesR ( const std::string& path, const std::string & exten = "*", bool addPath = true );
 			static std::vector<std::string> GetListFolders( const std::string& path, const std::string & exten = "*", bool addPath = true );
     };
+
+    /*
+     * Generation of a set of different colors by the following way:
+     * 1) generate more then need colors (in "factor" times) in RGB,
+     * 2) convert them to Lab,
+     * 3) choose the needed count of colors from the set that are more different from
+     *    each other,
+     * 4) convert the colors back to RGB
+     */
+    CV_EXPORTS void generateColors( std::vector<Scalar>& colors, size_t count, size_t factor=100 );
 }
 
 #include "opencv2/contrib/retina.hpp"

modules/contrib/src/gencolors.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) 2000-2008, Intel Corporation, all rights reserved.
+// Copyright (C) 2009, Willow Garage Inc., 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/core.hpp"
+#include "precomp.hpp"
+
+#include <iostream>
+
+using namespace cv;
+
+void downsamplePoints( const Mat& src, Mat& dst, size_t count )
+{
+    CV_Assert( count >= 2 );
+    CV_Assert( src.cols == 1 || src.rows == 1 );
+    CV_Assert( src.total() >= count );
+    CV_Assert( src.type() == CV_8UC3);
+
+    dst.create( 1, count, CV_8UC3 );
+    //TODO: optimize by exploiting symmetry in the distance matrix
+    Mat dists( src.total(), src.total(), CV_32FC1, Scalar(0) );
+    if( dists.empty() )
+        std::cerr << "Such big matrix cann't be created." << std::endl;
+
+    for( int i = 0; i < dists.rows; i++ )
+    {
+        for( int j = i; j < dists.cols; j++ )
+        {
+            float dist = norm(src.at<Point3_<uchar> >(i) - src.at<Point3_<uchar> >(j));
+            dists.at<float>(j, i) = dists.at<float>(i, j) = dist;
+        }
+    }
+
+    double maxVal;
+    Point maxLoc;
+    minMaxLoc(dists, 0, &maxVal, 0, &maxLoc);
+
+    dst.at<Point3_<uchar> >(0) = src.at<Point3_<uchar> >(maxLoc.x);
+    dst.at<Point3_<uchar> >(1) = src.at<Point3_<uchar> >(maxLoc.y);
+
+    Mat activedDists( 0, dists.cols, dists.type() );
+    Mat candidatePointsMask( 1, dists.cols, CV_8UC1, Scalar(255) );
+    activedDists.push_back( dists.row(maxLoc.y) );
+    candidatePointsMask.at<uchar>(0, maxLoc.y) = 0;
+
+    for( size_t i = 2; i < count; i++ )
+    {
+        activedDists.push_back(dists.row(maxLoc.x));
+        candidatePointsMask.at<uchar>(0, maxLoc.x) = 0;
+
+        Mat minDists;
+        reduce( activedDists, minDists, 0, CV_REDUCE_MIN );
+        minMaxLoc( minDists, 0, &maxVal, 0, &maxLoc, candidatePointsMask );
+        dst.at<Point3_<uchar> >(i) = src.at<Point3_<uchar> >(maxLoc.x);
+    }
+}
+
+void cv::generateColors( std::vector<Scalar>& colors, size_t count, size_t factor )
+{
+    if( count < 1 )
+        return;
+
+    colors.resize(count);
+
+    if( count == 1 )
+    {
+        colors[0] = Scalar(0,0,255); // red
+        return;
+    }
+    if( count == 2 )
+    {
+        colors[0] = Scalar(0,0,255); // red
+        colors[1] = Scalar(0,255,0); // green
+        return;
+    }
+
+    // Generate a set of colors in RGB space. A size of the set is severel times (=factor) larger then
+    // the needed count of colors.
+    Mat bgr( 1, count*factor, CV_8UC3 );
+    randu( bgr, 0, 256 );
+
+    // Convert the colors set to Lab space.
+    // Distances between colors in this space correspond a human perception.
+    Mat lab;
+    cvtColor( bgr, lab, CV_BGR2Lab);
+
+    // Subsample colors from the generated set so that
+    // to maximize the minimum distances between each other.
+    // Douglas-Peucker algorithm is used for this.
+    Mat lab_subset;
+    downsamplePoints( lab, lab_subset, count );
+
+    // Convert subsampled colors back to RGB
+    Mat bgr_subset;
+    cvtColor( lab_subset, bgr_subset, CV_Lab2BGR );
+
+    CV_Assert( bgr_subset.total() == count );
+    for( size_t i = 0; i < count; i++ )
+    {
+        Point3_<uchar> c = bgr_subset.at<Point3_<uchar> >(i);
+        colors[i] = Scalar(c.x, c.y, c.z);
+    }
+}