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comparison gnv-artifacts/src/main/java/de/intevation/gnv/utils/IndexBuffer.java @ 349:555483213f78

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Added buffer creator in index (i, j) space. gnv-artifacts/trunk@419 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Mon, 14 Dec 2009 14:36:43 +0000
parents
children b1f5f2a8840f
comparison
equal deleted inserted replaced
348:ec95d3248576 349:555483213f78
1 package de.intevation.gnv.utils;
2
3 import java.awt.geom.Point2D;
4
5 import java.awt.Point;
6
7 import java.util.List;
8
9 /**
10 * Create buffers around integer pairs (i_1..n), j_1..n).
11 *
12 * @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
13 */
14 public class IndexBuffer
15 {
16 public static final double EPSILON = 1e-6d;
17 public static final double OFFSET = 1.0d;
18
19 public static final String I_COLUMN = "IPOSITION";
20 public static final String J_COLUMN = "JPOSITION";
21
22 public static final class Segment {
23
24 private Segment next;
25
26 private Point2D.Double n;
27 private double d1;
28 private double d2;
29
30 private int iMin;
31 private int iMax;
32
33 private int jMin;
34 private int jMax;
35
36 public Segment(Point a, Point b, Segment next) {
37
38 this.next = next;
39
40 iMin = Math.min(a.x, b.x)-1;
41 iMax = Math.max(a.x, b.x)+1;
42
43 jMin = Math.min(a.y, b.y)-1;
44 jMax = Math.max(a.y, b.y)+1;
45
46 if (a.x > b.x) {
47 Point p = a; a = b; b = p;
48 }
49
50 Point2D.Double p1, p2, p3;
51
52 if (a.y < b.y) {
53 p1 = new Point2D.Double(a.x - OFFSET, a.y + 1 + OFFSET);
54 p2 = new Point2D.Double(b.x - OFFSET, b.y + 1 + OFFSET);
55 p3 = new Point2D.Double(a.x + 1 + OFFSET, a.y - OFFSET);
56 }
57 else {
58 p1 = new Point2D.Double(a.x + 1 + OFFSET, a.y + 1 + OFFSET);
59 p2 = new Point2D.Double(b.x + 1 + OFFSET, b.y + 1 + OFFSET);
60 p3 = new Point2D.Double(b.x - OFFSET, b.y - OFFSET);
61 }
62
63 n = normalize(orthogonal(sub(p1, p2)));
64
65 d1 = dot(n, p1);
66 d2 = dot(n, p3);
67
68 if (d1 > d2) {
69 double d = d1;
70 d1 = d2;
71 d2 = d;
72 }
73 }
74
75 public boolean check(int i, int j) {
76 if (i < iMin || i > iMax || j < jMin || j > jMax) {
77 return false;
78 }
79 double v = dot(n, i, j);
80 return v >= d1 && v <= d2;
81 }
82
83 public void toWhereClause(StringBuilder sb, String iColumn, String jColumn) {
84 sb.append('(')
85 .append(iColumn).append(" >= ").append(iMin).append(" AND ")
86 .append(iColumn).append(" <= ").append(iMax).append(" AND ")
87 .append(jColumn).append(" >= ").append(jMin).append(" AND ")
88 .append(jColumn).append(" <= ").append(jMax).append(" AND (")
89 .append(n.x).append('*').append(iColumn).append(" + ")
90 .append(n.y).append('*').append(jColumn)
91 .append(") BETWEEN ").append(d1).append(" AND ").append(d2).append(')');
92 }
93 } // class Segment
94
95 protected Segment head;
96
97 protected String iColumn;
98 protected String jColumn;
99
100 public IndexBuffer(List<? extends Point> points) {
101 this(points, I_COLUMN, J_COLUMN);
102 }
103
104 public IndexBuffer(List<? extends Point> points, String iColumn, String jColumn) {
105 this.iColumn = iColumn;
106 this.jColumn = jColumn;
107
108 for (int i = 1, N = points.size(); i < N; ++i) {
109 Point p1 = (Point)points.get(i-1);
110 Point p2 = (Point)points.get(i);
111 head = new Segment(p1, p2, head);
112 }
113 }
114
115 public boolean check(int i, int j) {
116
117 Segment current = head;
118 while (current != null) {
119 if (current.check(i, j)) {
120 return true;
121 }
122 current = current.next;
123 }
124 return false;
125 }
126
127 public String toWhereClause() {
128
129 StringBuilder sb = new StringBuilder();
130
131 Segment current = head;
132
133 while (current != null) {
134 if (current != head) {
135 sb.append(" OR ");
136 }
137 current.toWhereClause(sb, iColumn, jColumn);
138 current = current.next;
139 }
140
141 return sb.toString();
142 }
143
144 public static Point2D.Double sub(Point2D.Double p1, Point2D.Double p2) {
145 return new Point2D.Double(p1.x - p2.x, p1.y - p2.y);
146 }
147
148 public static final double dot(Point2D.Double p1, Point2D.Double p2) {
149 return p1.x*p2.x + p1.y*p2.y;
150 }
151
152 public static final double dot(Point2D.Double p1, double x, double y) {
153 return p1.x*x + p1.y*y;
154 }
155
156 public static final Point2D.Double scale(Point2D.Double p, double s) {
157 return new Point2D.Double(s*p.x, s*p.y);
158 }
159
160 public static final Point2D.Double normalize(Point2D.Double p) {
161 double len2 = Math.sqrt(dot(p, p));
162 return len2 > EPSILON ? scale(p, 1d/len2) : p;
163 }
164
165 public static final Point2D.Double orthogonal(Point2D.Double p) {
166 return new Point2D.Double(p.y, -p.x);
167 }
168 }
169 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8:
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