More work on export tab.

[rails.git] / lib / bounding_box.rb

diff --git a/lib/bounding_box.rb b/lib/bounding_box.rb
new file mode 100644 (file)
index 0000000..d943768
--- /dev/null
+++ b/lib/bounding_box.rb
@@ -0,0 +1,72 @@
+class BoundingBox
+  def initialize(min_lon, min_lat, max_lon, max_lat)
+    @bbox = [min_lon.to_f, min_lat.to_f, max_lon.to_f, max_lat.to_f]
+  end
+
+  def self.from_s(s)
+    BoundingBox.new(s.split(/,/))
+  end
+
+  def min_lon
+    @bbox[0]
+  end
+
+  def min_lon=(min_lon)
+    @bbox[0] = min_lon
+  end
+
+  def min_lat
+    @bbox[1]
+  end
+
+  def min_lat=(min_lat)
+    @bbox[1] = min_lat
+  end
+
+  def max_lon
+    @bbox[2]
+  end
+
+  def max_lon=(max_lon)
+    @bbox[2] = max_lon
+  end
+
+  def max_lat
+    @bbox[3]
+  end
+
+  def max_lat=(max_lat)
+    @bbox[3] = max_lat
+  end
+
+  def centre_lon
+    (@bbox[0] + @bbox[2]) / 2.0
+  end
+
+  def centre_lat
+    (@bbox[1] + @bbox[3]) / 2.0
+  end
+
+  def width
+    @bbox[2] - @bbox[0]
+  end
+
+  def height
+    @bbox[3] - @bbox[1]
+  end
+
+  def slippy_width(zoom)
+    width * 256.0 * 2.0 ** zoom / 360.0
+  end
+
+  def slippy_height(zoom)
+    min = min_lat * Math::PI / 180.0
+    max = max_lat * Math::PI / 180.0
+
+    Math.log((Math.tan(max) + 1.0 / Math.cos(max)) / (Math.tan(min) + 1.0 / Math.cos(min))) * 128.0 * 2.0 ** zoom / Math::PI
+  end
+
+  def to_s
+    return @bbox.join(",")
+  end
+end