Pulled tile calculations out into a handy utility method.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3082 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/geom/GeomUtil.java

@@ -1,5 +1,5 @@
 //
-// $Id: GeomUtil.java,v 1.7 2004/02/25 14:42:30 mdb Exp $
+// $Id: GeomUtil.java,v 1.8 2004/08/17 00:48:40 mdb Exp $
 
 package com.threerings.geom;
 
@@ -207,4 +207,27 @@ public class GeomUtil
         }
         return source;
     }
+
+    /**
+     * Returns the rectangle containing the specified tile in the supplied
+     * larger rectangle. Tiles go from left to right, top to bottom.
+     */
+    public static Rectangle getTile (
+        int width, int height, int tileWidth, int tileHeight, int tileIndex)
+    {
+        // figure out from whence to crop the tile
+        int tilesPerRow = width / tileWidth;
+
+        // if we got a bogus region, return bogus tile bounds
+        if (tilesPerRow == 0) {
+            return new Rectangle(0, 0, width, height);
+        }
+
+        int row = tileIndex / tilesPerRow;
+        int col = tileIndex % tilesPerRow;
+
+	// crop the tile-sized image chunk from the full image
+        return new Rectangle(
+            tileWidth*col, tileHeight*row, tileWidth, tileHeight);
+    }
 }