1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 ///////////////////////////// 18 // Geometry.h 19 // $Id: Geometry.h,v 1.2 2011/06/17 13:35:48 mbansal Exp $ 20 21 #pragma once 22 #include "MosaicTypes.h" 23 24 /////////////////////////////////////////////////////////////// 25 ///////////////// BEG GLOBAL ROUTINES ///////////////////////// 26 /////////////////////////////////////////////////////////////// 27 28 29 inline double hypotSq(double a, double b) 30 { 31 return ((a)*(a)+(b)*(b)); 32 } 33 34 inline void ClipRect(double x, double y, BlendRect &brect) 35 { 36 if (y < brect.bot) brect.bot = y; 37 if (y > brect.top) brect.top = y; 38 if (x < brect.lft) brect.lft = x; 39 if (x > brect.rgt) brect.rgt = x; 40 } 41 42 inline void ClipRect(BlendRect rrect, BlendRect &brect) 43 { 44 if (rrect.bot < brect.bot) brect.bot = rrect.bot; 45 if (rrect.top > brect.top) brect.top = rrect.top; 46 if (rrect.lft < brect.lft) brect.lft = rrect.lft; 47 if (rrect.rgt > brect.rgt) brect.rgt = rrect.rgt; 48 } 49 50 // Clip x to be within [-border,width+border-1] 51 inline void clipToSegment(int &x, int width, int border) 52 { 53 if(x < -border) 54 x = -border; 55 else if(x >= width+border) 56 x = width + border - 1; 57 } 58 59 // Return true if x within [-border,width+border-1] 60 inline bool inSegment(int x, int width, int border) 61 { 62 return (x >= -border && x < width + border - 1); 63 } 64 65 inline void FindTriangleCentroid(double x0, double y0, double x1, double y1, 66 double x2, double y2, 67 double &mass, double ¢X, double ¢Y) 68 { 69 // Calculate the centroid of the triangle 70 centX = (x0 + x1 + x2) / 3.0; 71 centY = (y0 + y1 + y2) / 3.0; 72 73 // Calculate 2*Area for the triangle 74 if (y0 == y2) 75 { 76 if (x0 == x1) 77 { 78 mass = fabs((y1 - y0) * (x2 - x0)); // Special case 1a 79 } 80 else 81 { 82 mass = fabs((y1 - y0) * (x1 - x0)); // Special case 1b 83 } 84 } 85 else if (x0 == x2) 86 { 87 if (x0 == x1) 88 { 89 mass = fabs((x2 - x0) * (y2 - y0)); // Special case 2a 90 } 91 else 92 { 93 mass = fabs((x1 - x0) * (y2 - y0)); // Special case 2a 94 } 95 } 96 else if (x1 == x2) 97 { 98 mass = fabs((x1 - x0) * (y2 - y0)); // Special case 3 99 } 100 else 101 { 102 // Calculate line equation from x0,y0 to x2,y2 103 double dx = x2 - x0; 104 double dy = y2 - y0; 105 // Calculate the length of the side 106 double len1 = sqrt(dx * dx + dy * dy); 107 double m1 = dy / dx; 108 double b1 = y0 - m1 * x0; 109 // Calculate the line that goes through x1,y1 and is perpendicular to 110 // the other line 111 double m2 = 1.0 / m1; 112 double b2 = y1 - m2 * x1; 113 // Calculate the intersection of the two lines 114 if (fabs( m1 - m2 ) > 1.e-6) 115 { 116 double x = (b2 - b1) / (m1 - m2); 117 // the mass is the base * height 118 dx = x1 - x; 119 dy = y1 - m1 * x + b1; 120 mass = len1 * sqrt(dx * dx + dy * dy); 121 } 122 else 123 { 124 mass = fabs( (y1 - y0) * (x2 - x0) ); 125 } 126 } 127 } 128 129 inline void FindQuadCentroid(double x0, double y0, double x1, double y1, double x2, double y2, double x3, double y3, 130 double ¢X, double ¢Y) 131 132 { 133 // To find the centroid: 134 // 1) Divide the quadrilateral into two triangles by scribing a diagonal 135 // 2) Calculate the centroid of each triangle (the intersection of the angle bisections). 136 // 3) Find the centroid of the quad by weighting each triangle centroids by their area. 137 138 // Calculate the corner points 139 double z; 140 141 // The quad is split from x0,y0 to x2,y2 142 double mass1, mass2, cent1x, cent2x, cent1y, cent2y; 143 FindTriangleCentroid(x0, y0, x1, y1, x2, y2, mass1, cent1x, cent1y); 144 FindTriangleCentroid(x0, y0, x3, y3, x2, y2, mass2, cent2x, cent2y); 145 146 // determine position of quad centroid 147 z = mass2 / (mass1 + mass2); 148 centX = cent1x + (cent2x - cent1x) * z; 149 centY = cent1y + (cent2y - cent1y) * z; 150 } 151 152 /////////////////////////////////////////////////////////////// 153 ////////////////// END GLOBAL ROUTINES //////////////////////// 154 /////////////////////////////////////////////////////////////// 155 156 157
