JAL-3026 srcjar files for VARNA and log4j

[jalview.git] / srcjar / fr / orsay / lri / varna / models / geom / LinesIntersect.java

diff --git a/srcjar/fr/orsay/lri/varna/models/geom/LinesIntersect.java b/srcjar/fr/orsay/lri/varna/models/geom/LinesIntersect.java
new file mode 100644 (file)
index 0000000..fa238fe
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+++ b/srcjar/fr/orsay/lri/varna/models/geom/LinesIntersect.java
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+/**
+ * File written by Raphael Champeimont
+ * UMR 7238 Genomique des Microorganismes
+ */
+package fr.orsay.lri.varna.models.geom;
+
+import java.awt.geom.Line2D;
+import java.awt.geom.Point2D;
+
+/**
+ * Like Line2D.Double.linesIntersect() of the standard library, but without the bug!
+ * See this: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6457965
+ * This result is incorrect with, for example:
+ * System.out.println(Line2D.Double.linesIntersect(179.2690296114372, 1527.2309703885628, 150.9847583639753, 1498.946699141101, 94.4162158690515, 1442.378156646177, 66.1319446215896, 1414.0938853987152));
+ * (real example observed on an RNA with no intersection at all)
+ * This lines obviously don't intersect (both X and Y ranges are clearly disjoint!)
+ * but linesIntersect() returns true.
+ * Here we provide a bug-free function.
+ */
+public class LinesIntersect {
+       /**
+        * Returns whether segment from (x1,y1) to (x2,y2)
+        * intersect with segment from (x3,y3) to (x4,y4).
+        */
+       public static boolean linesIntersect(
+                       double x1,
+            double y1,
+            double x2,
+            double y2,
+            double x3,
+            double y3,
+            double x4,
+            double y4) {
+               
+             double denom = (y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1);
+             if (denom == 0.0) { // Lines are parallel.
+                return false;
+             }
+             double ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denom;
+             double ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denom;
+             return (ua >= 0.0 && ua <= 1.0 && ub >= 0.0 && ub <= 1.0);
+       }
+       
+       /**
+        * Returns whether segment from p1 to p2 intersects segment from p3 to p4.
+        */
+       public static boolean linesIntersect(
+                       Point2D.Double p1,
+                       Point2D.Double p2,
+                       Point2D.Double p3,
+                       Point2D.Double p4) {
+               return linesIntersect(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y);
+       }
+       
+       /**
+        * Returns whether the two segment intersect.
+        */
+       public static boolean linesIntersect(Line2D.Double line1, Line2D.Double line2) {
+               return linesIntersect(
+                               line1.x1, line1.y1, line1.x2, line1.y2,
+                               line2.x1, line2.y1, line2.x2, line2.y2);
+       }
+       
+       
+       private static void test(
+                       double x1,
+            double y1,
+            double x2,
+            double y2,
+            double x3,
+            double y3,
+            double x4,
+            double y4,
+            boolean expectedResult) {
+               boolean a = linesIntersect(x1, y1, x2, y2, x3, y3, x4, y4);
+               boolean b = Line2D.Double.linesIntersect(x1, y1, x2, y2, x3, y3, x4, y4);
+               System.out.println("ours says " + a + " which is " + (a == expectedResult ? "correct" : "INCORRECT") +
+                               " / Line2D.Double says " + b + " which is " + (b == expectedResult ? "correct" : "INCORRECT"));
+       }
+       
+       public static void main(String[] args) {
+               test(179.2690296114372, 1527.2309703885628, 150.9847583639753, 1498.946699141101, 94.4162158690515, 1442.378156646177, 66.1319446215896, 1414.0938853987152, false);
+               test(0, 0, 0, 0, 1, 1, 1, 1, false);
+               test(0, 0, 0.5, 0.5, 1, 1, 2, 2, false);
+               test(0, 0, 2, 2, 0, 2, 2, 0, true);
+               test(0, 0, 2, 2, 4, 0, 3, 2, false);
+       }
+}