1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.data.osm.visitor.paint;
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3 |
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4 | import static java.awt.geom.Rectangle2D.OUT_BOTTOM;
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5 | import static java.awt.geom.Rectangle2D.OUT_LEFT;
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6 | import static java.awt.geom.Rectangle2D.OUT_RIGHT;
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7 | import static java.awt.geom.Rectangle2D.OUT_TOP;
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8 |
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9 | import java.awt.Rectangle;
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10 | import java.awt.geom.Point2D;
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11 | import java.awt.geom.Rectangle2D;
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12 |
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13 | /**
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14 | * Computes the part of a line that is visible in a given rectangle.
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15 | * Using int leads to overflow, so we need long int.
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16 | */
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17 | public class LineClip {
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18 | private Point2D p1, p2;
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19 | private final Rectangle2D clipBounds;
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20 |
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21 | /**
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22 | * Constructs a new {@code LineClip}.
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23 | * @param p1 start point of the clipped line
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24 | * @param p2 end point of the clipped line
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25 | * @param clipBounds Clip bounds
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26 | * @since 10826
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27 | */
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28 | public LineClip(Point2D p1, Point2D p2, Rectangle2D clipBounds) {
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29 | this.p1 = p1;
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30 | this.p2 = p2;
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31 | this.clipBounds = clipBounds;
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32 | }
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33 |
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34 | /**
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35 | * run the clipping algorithm
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36 | * @return true if the some parts of the line lies within the clip bounds
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37 | */
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38 | public boolean execute() {
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39 | if (clipBounds == null) {
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40 | return false;
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41 | }
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42 | return cohenSutherland(p1.getX(), p1.getY(), p2.getX(), p2.getY(), clipBounds.getMinX(), clipBounds.getMinY(),
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43 | clipBounds.getMaxX(), clipBounds.getMaxY());
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44 | }
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45 |
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46 | /**
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47 | * @return start point of the clipped line
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48 | * @since 10826
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49 | */
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50 | public Point2D getP1() {
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51 | return p1;
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52 | }
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53 |
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54 | /**
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55 | * @return end point of the clipped line
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56 | * @since 10826
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57 | */
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58 | public Point2D getP2() {
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59 | return p2;
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60 | }
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61 |
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62 | /**
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63 | * Cohen–Sutherland algorithm.
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64 | * See <a href="https://en.wikipedia.org/wiki/Cohen%E2%80%93Sutherland_algorithm">Wikipedia article</a>
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65 | * @param x1 X coordinate of first point
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66 | * @param y1 Y coordinate of first point
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67 | * @param x2 X coordinate of second point
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68 | * @param y2 Y coordinate of second point
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69 | * @param xmin minimal X coordinate
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70 | * @param ymin minimal Y coordinate
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71 | * @param xmax maximal X coordinate
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72 | * @param ymax maximal Y coordinate
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73 | * @return true, if line is visible in the given clip region
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74 | */
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75 | private boolean cohenSutherland(double x1, double y1, double x2, double y2, double xmin, double ymin, double xmax, double ymax) {
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76 | int outcode0, outcode1, outcodeOut;
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77 | boolean accept = false;
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78 | boolean done = false;
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79 |
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80 | outcode0 = computeOutCode(x1, y1, xmin, ymin, xmax, ymax);
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81 | outcode1 = computeOutCode(x2, y2, xmin, ymin, xmax, ymax);
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82 |
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83 | do {
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84 | if ((outcode0 | outcode1) == 0) {
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85 | accept = true;
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86 | done = true;
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87 | } else if ((outcode0 & outcode1) > 0) {
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88 | done = true;
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89 | } else {
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90 | double x = 0;
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91 | double y = 0;
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92 | outcodeOut = outcode0 != 0 ? outcode0 : outcode1;
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93 | if ((outcodeOut & OUT_TOP) != 0) {
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94 | x = x1 + (x2 - x1) * (ymax - y1)/(y2 - y1);
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95 | y = ymax;
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96 | } else if ((outcodeOut & OUT_BOTTOM) != 0) {
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97 | x = x1 + (x2 - x1) * (ymin - y1)/(y2 - y1);
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98 | y = ymin;
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99 | } else if ((outcodeOut & OUT_RIGHT) != 0) {
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100 | y = y1 + (y2 - y1) * (xmax - x1)/(x2 - x1);
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101 | x = xmax;
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102 | } else if ((outcodeOut & OUT_LEFT) != 0) {
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103 | y = y1 + (y2 - y1) * (xmin - x1)/(x2 - x1);
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104 | x = xmin;
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105 | }
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106 | if (outcodeOut == outcode0) {
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107 | x1 = x;
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108 | y1 = y;
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109 | outcode0 = computeOutCode(x1, y1, xmin, ymin, xmax, ymax);
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110 | } else {
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111 | x2 = x;
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112 | y2 = y;
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113 | outcode1 = computeOutCode(x2, y2, xmin, ymin, xmax, ymax);
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114 | }
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115 | }
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116 | }
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117 | while (!done);
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118 |
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119 | if (accept) {
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120 | p1 = new Point2D.Double(x1, y1);
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121 | p2 = new Point2D.Double(x2, y2);
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122 | return true;
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123 | }
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124 | return false;
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125 | }
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126 |
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127 | /**
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128 | * The outcode of the point.
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129 | * We cannot use {@link Rectangle#outcode} since it does not work with long ints.
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130 | * @param x X coordinate
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131 | * @param y Y coordinate
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132 | * @param xmin minimal X coordinate
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133 | * @param ymin minimal Y coordinate
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134 | * @param xmax maximal X coordinate
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135 | * @param ymax maximal Y coordinate
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136 | * @return outcode
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137 | */
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138 | private static int computeOutCode(double x, double y, double xmin, double ymin, double xmax, double ymax) {
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139 | int code = 0;
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140 | // ignore rounding errors.
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141 | if (y > ymax + 1e-10) {
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142 | code |= OUT_TOP;
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143 | } else if (y < ymin - 1e-10) {
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144 | code |= OUT_BOTTOM;
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145 | }
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146 | if (x > xmax + 1e-10) {
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147 | code |= OUT_RIGHT;
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148 | } else if (x < xmin - 1e-10) {
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149 | code |= OUT_LEFT;
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150 | }
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151 | return code;
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152 | }
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153 | }
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