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415 lines
12 KiB
C++
415 lines
12 KiB
C++
/*M///////////////////////////////////////////////////////////////////////////////////////
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//
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// IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
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//
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// By downloading, copying, installing or using the software you agree to this license.
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// If you do not agree to this license, do not download, install,
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// copy or use the software.
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//
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//
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// License Agreement
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// For Open Source Computer Vision Library
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//
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// Copyright (C) 2000, Intel Corporation, all rights reserved.
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// Third party copyrights are property of their respective owners.
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//
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// Redistribution and use in source and binary forms, with or without modification,
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// are permitted provided that the following conditions are met:
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//
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// * Redistribution's of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// * Redistribution's in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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//
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// * The name of OpenCV Foundation may not be used to endorse or promote products
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// derived from this software without specific prior written permission.
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//
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// This software is provided by the copyright holders and contributors "as is" and
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// any express or implied warranties, including, but not limited to, the implied
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// warranties of merchantability and fitness for a particular purpose are disclaimed.
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// In no event shall the OpenCV Foundation or contributors be liable for any direct,
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// indirect, incidental, special, exemplary, or consequential damages
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// (including, but not limited to, procurement of substitute goods or services;
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// loss of use, data, or profits; or business interruption) however caused
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// and on any theory of liability, whether in contract, strict liability,
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// or tort (including negligence or otherwise) arising in any way out of
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// the use of this software, even if advised of the possibility of such damage.
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//
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//M*/
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#include "precomp.hpp"
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namespace cv
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{
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struct MinAreaState
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{
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int bottom;
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int left;
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float height;
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float width;
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float base_a;
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float base_b;
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};
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enum { CALIPERS_MAXHEIGHT=0, CALIPERS_MINAREARECT=1, CALIPERS_MAXDIST=2 };
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/*F///////////////////////////////////////////////////////////////////////////////////////
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// Name: rotatingCalipers
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// Purpose:
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// Rotating calipers algorithm with some applications
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//
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// Context:
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// Parameters:
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// points - convex hull vertices ( any orientation )
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// n - number of vertices
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// mode - concrete application of algorithm
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// can be CV_CALIPERS_MAXDIST or
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// CV_CALIPERS_MINAREARECT
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// left, bottom, right, top - indexes of extremal points
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// out - output info.
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// In case CV_CALIPERS_MAXDIST it points to float value -
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// maximal height of polygon.
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// In case CV_CALIPERS_MINAREARECT
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// ((CvPoint2D32f*)out)[0] - corner
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// ((CvPoint2D32f*)out)[1] - vector1
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// ((CvPoint2D32f*)out)[0] - corner2
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//
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// ^
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// |
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// vector2 |
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// |
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// |____________\
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// corner /
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// vector1
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//
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// Returns:
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// Notes:
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//F*/
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/* we will use usual cartesian coordinates */
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static void rotatingCalipers( const Point2f* points, int n, int mode, float* out )
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{
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float minarea = FLT_MAX;
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float max_dist = 0;
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char buffer[32] = {};
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int i, k;
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AutoBuffer<float> abuf(n*3);
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float* inv_vect_length = abuf;
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Point2f* vect = (Point2f*)(inv_vect_length + n);
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int left = 0, bottom = 0, right = 0, top = 0;
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int seq[4] = { -1, -1, -1, -1 };
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/* rotating calipers sides will always have coordinates
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(a,b) (-b,a) (-a,-b) (b, -a)
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*/
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/* this is a first base bector (a,b) initialized by (1,0) */
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float orientation = 0;
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float base_a;
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float base_b = 0;
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float left_x, right_x, top_y, bottom_y;
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Point2f pt0 = points[0];
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left_x = right_x = pt0.x;
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top_y = bottom_y = pt0.y;
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for( i = 0; i < n; i++ )
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{
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double dx, dy;
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if( pt0.x < left_x )
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left_x = pt0.x, left = i;
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if( pt0.x > right_x )
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right_x = pt0.x, right = i;
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if( pt0.y > top_y )
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top_y = pt0.y, top = i;
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if( pt0.y < bottom_y )
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bottom_y = pt0.y, bottom = i;
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Point2f pt = points[(i+1) & (i+1 < n ? -1 : 0)];
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dx = pt.x - pt0.x;
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dy = pt.y - pt0.y;
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vect[i].x = (float)dx;
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vect[i].y = (float)dy;
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inv_vect_length[i] = (float)(1./std::sqrt(dx*dx + dy*dy));
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pt0 = pt;
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}
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// find convex hull orientation
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{
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double ax = vect[n-1].x;
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double ay = vect[n-1].y;
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for( i = 0; i < n; i++ )
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{
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double bx = vect[i].x;
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double by = vect[i].y;
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double convexity = ax * by - ay * bx;
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if( convexity != 0 )
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{
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orientation = (convexity > 0) ? 1.f : (-1.f);
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break;
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}
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ax = bx;
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ay = by;
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}
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CV_Assert( orientation != 0 );
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}
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base_a = orientation;
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/*****************************************************************************************/
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/* init calipers position */
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seq[0] = bottom;
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seq[1] = right;
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seq[2] = top;
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seq[3] = left;
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/*****************************************************************************************/
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/* Main loop - evaluate angles and rotate calipers */
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/* all of edges will be checked while rotating calipers by 90 degrees */
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for( k = 0; k < n; k++ )
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{
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/* sinus of minimal angle */
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/*float sinus;*/
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/* compute cosine of angle between calipers side and polygon edge */
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/* dp - dot product */
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float dp[4] = {
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+base_a * vect[seq[0]].x + base_b * vect[seq[0]].y,
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-base_b * vect[seq[1]].x + base_a * vect[seq[1]].y,
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-base_a * vect[seq[2]].x - base_b * vect[seq[2]].y,
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+base_b * vect[seq[3]].x - base_a * vect[seq[3]].y,
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};
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float maxcos = dp[0] * inv_vect_length[seq[0]];
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/* number of calipers edges, that has minimal angle with edge */
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int main_element = 0;
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/* choose minimal angle */
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for ( i = 1; i < 4; ++i )
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{
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float cosalpha = dp[i] * inv_vect_length[seq[i]];
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if (cosalpha > maxcos)
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{
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main_element = i;
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maxcos = cosalpha;
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}
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}
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/*rotate calipers*/
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{
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//get next base
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int pindex = seq[main_element];
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float lead_x = vect[pindex].x*inv_vect_length[pindex];
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float lead_y = vect[pindex].y*inv_vect_length[pindex];
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switch( main_element )
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{
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case 0:
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base_a = lead_x;
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base_b = lead_y;
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break;
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case 1:
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base_a = lead_y;
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base_b = -lead_x;
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break;
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case 2:
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base_a = -lead_x;
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base_b = -lead_y;
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break;
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case 3:
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base_a = -lead_y;
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base_b = lead_x;
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break;
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default:
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CV_Error(CV_StsError, "main_element should be 0, 1, 2 or 3");
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}
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}
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/* change base point of main edge */
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seq[main_element] += 1;
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seq[main_element] = (seq[main_element] == n) ? 0 : seq[main_element];
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switch (mode)
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{
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case CALIPERS_MAXHEIGHT:
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{
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/* now main element lies on edge alligned to calipers side */
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/* find opposite element i.e. transform */
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/* 0->2, 1->3, 2->0, 3->1 */
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int opposite_el = main_element ^ 2;
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float dx = points[seq[opposite_el]].x - points[seq[main_element]].x;
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float dy = points[seq[opposite_el]].y - points[seq[main_element]].y;
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float dist;
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if( main_element & 1 )
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dist = (float)fabs(dx * base_a + dy * base_b);
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else
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dist = (float)fabs(dx * (-base_b) + dy * base_a);
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if( dist > max_dist )
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max_dist = dist;
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}
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break;
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case CALIPERS_MINAREARECT:
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/* find area of rectangle */
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{
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float height;
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float area;
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/* find vector left-right */
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float dx = points[seq[1]].x - points[seq[3]].x;
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float dy = points[seq[1]].y - points[seq[3]].y;
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/* dotproduct */
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float width = dx * base_a + dy * base_b;
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/* find vector left-right */
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dx = points[seq[2]].x - points[seq[0]].x;
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dy = points[seq[2]].y - points[seq[0]].y;
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/* dotproduct */
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height = -dx * base_b + dy * base_a;
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area = width * height;
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if( area <= minarea )
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{
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float *buf = (float *) buffer;
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minarea = area;
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/* leftist point */
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((int *) buf)[0] = seq[3];
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buf[1] = base_a;
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buf[2] = width;
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buf[3] = base_b;
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buf[4] = height;
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/* bottom point */
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((int *) buf)[5] = seq[0];
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buf[6] = area;
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}
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}
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break;
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} /*switch */
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} /* for */
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switch (mode)
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{
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case CALIPERS_MINAREARECT:
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{
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float *buf = (float *) buffer;
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float A1 = buf[1];
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float B1 = buf[3];
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float A2 = -buf[3];
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float B2 = buf[1];
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float C1 = A1 * points[((int *) buf)[0]].x + points[((int *) buf)[0]].y * B1;
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float C2 = A2 * points[((int *) buf)[5]].x + points[((int *) buf)[5]].y * B2;
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float idet = 1.f / (A1 * B2 - A2 * B1);
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float px = (C1 * B2 - C2 * B1) * idet;
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float py = (A1 * C2 - A2 * C1) * idet;
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out[0] = px;
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out[1] = py;
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out[2] = A1 * buf[2];
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out[3] = B1 * buf[2];
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out[4] = A2 * buf[4];
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out[5] = B2 * buf[4];
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}
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break;
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case CALIPERS_MAXHEIGHT:
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{
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out[0] = max_dist;
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}
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break;
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}
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}
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}
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cv::RotatedRect cv::minAreaRect( InputArray _points )
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{
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CV_INSTRUMENT_REGION()
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Mat hull;
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Point2f out[3];
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RotatedRect box;
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convexHull(_points, hull, true, true);
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if( hull.depth() != CV_32F )
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{
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Mat temp;
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hull.convertTo(temp, CV_32F);
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hull = temp;
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}
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int n = hull.checkVector(2);
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const Point2f* hpoints = hull.ptr<Point2f>();
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if( n > 2 )
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{
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rotatingCalipers( hpoints, n, CALIPERS_MINAREARECT, (float*)out );
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box.center.x = out[0].x + (out[1].x + out[2].x)*0.5f;
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box.center.y = out[0].y + (out[1].y + out[2].y)*0.5f;
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box.size.width = (float)std::sqrt((double)out[1].x*out[1].x + (double)out[1].y*out[1].y);
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box.size.height = (float)std::sqrt((double)out[2].x*out[2].x + (double)out[2].y*out[2].y);
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box.angle = (float)atan2( (double)out[1].y, (double)out[1].x );
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}
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else if( n == 2 )
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{
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box.center.x = (hpoints[0].x + hpoints[1].x)*0.5f;
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box.center.y = (hpoints[0].y + hpoints[1].y)*0.5f;
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double dx = hpoints[1].x - hpoints[0].x;
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double dy = hpoints[1].y - hpoints[0].y;
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box.size.width = (float)std::sqrt(dx*dx + dy*dy);
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box.size.height = 0;
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box.angle = (float)atan2( dy, dx );
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}
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else
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{
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if( n == 1 )
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box.center = hpoints[0];
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}
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box.angle = (float)(box.angle*180/CV_PI);
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return box;
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}
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CV_IMPL CvBox2D
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cvMinAreaRect2( const CvArr* array, CvMemStorage* /*storage*/ )
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{
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cv::AutoBuffer<double> abuf;
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cv::Mat points = cv::cvarrToMat(array, false, false, 0, &abuf);
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cv::RotatedRect rr = cv::minAreaRect(points);
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return (CvBox2D)rr;
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}
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void cv::boxPoints(cv::RotatedRect box, OutputArray _pts)
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{
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CV_INSTRUMENT_REGION()
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_pts.create(4, 2, CV_32F);
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Mat pts = _pts.getMat();
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box.points(pts.ptr<Point2f>());
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}
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