From 78588aa8ea1876b0d6664f56d17d60723be9ae9e Mon Sep 17 00:00:00 2001
From: euzuro <euzuro@metacarta.com>
Date: Mon, 22 May 2006 09:55:20 +0000
Subject: [PATCH] adding getPixelFromLonLat() function to Map.js -- the code is
 lifted from OpenLayers.Layer.Marker's drawMarker() function. also test added
 to ensure both translation functions return valid objects and that going back
 and forth is consistent. Note that i only test pixel-lonlat-pixel, because
 going from lonlat-pixel-lonlat there is loss due to the rounding in the
 lonlat-pixel phase

git-svn-id: http://svn.openlayers.org/trunk/openlayers@246 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
---
 lib/OpenLayers/Map.js | 17 +++++++++++++++++
 tests/test_Map.html   | 19 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index 510b1b133d..f040c9e167 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -271,6 +271,23 @@ OpenLayers.Map.prototype = {
                                      center.lat - delta_y * res); 
     },
 
+    /**
+    * @param {OpenLayers.LonLat} lonlat
+    *
+    * @returns An OpenLayers.Pixel which is the passed-in OpenLayers.LonLat, 
+    *          translated into screen pixels given the current extent 
+    *          and resolution
+    * @type OpenLayers.Pixel
+    */
+    getPixelFromLonLat: function (lonlat) {
+        var resolution = this.getResolution();
+        var extent = this.getExtent();
+        return new OpenLayers.Pixel(
+                       Math.round(1/resolution * (lonlat.lon - extent.left)),
+                       Math.round(1/resolution * (extent.top - lonlat.lat))
+                       );    
+    },
+
     /**
     * @param {OpenLayers.LonLat} lonlat
     * @param {int} zoom
diff --git a/tests/test_Map.html b/tests/test_Map.html
index e3d144d3cc..fa99cb3adf 100644
--- a/tests/test_Map.html
+++ b/tests/test_Map.html
@@ -113,6 +113,25 @@
 
     }
 
+    function test_08_Map_px_lonlat_translation (t) {
+        t.plan( 3 );    
+        map = new OpenLayers.Map($('map'));
+        map.setCenter(new OpenLayers.LonLat(0, 0), 0);
+ 
+        var pixel = new OpenLayers.Pixel(50,150);
+        var lonlat = map.getLonLatFromPixel(pixel);
+        t.ok( lonlat instanceof OpenLayers.LonLat, "getLonLatFromPixel returns valid OpenLayers.LonLat" );
+
+        var newPixel = map.getPixelFromLonLat(lonlat);
+        t.ok( newPixel instanceof OpenLayers.Pixel, "getPixelFromLonLat returns valid OpenLayers.Pixel" );
+
+        // WARNING!!!  I'm faily sure that the following test's validity 
+        //             depends highly on rounding and the resolution. For now,
+        //             in the default case, it seems to work. This may not 
+        //             always be so.
+        t.ok( newPixel.equals(pixel), "Translation to pixel and back to lonlat is consistent");
+    }
+
     function test_99_Map_destroy (t) {
         t.plan( 2 );    
         map = new OpenLayers.Map($('map'));