Index: trunk/src/org/openstreetmap/josm/gui/mappaint/MapImage.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/MapImage.java	(revision 4823)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/MapImage.java	(revision 4823)
@@ -0,0 +1,63 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.gui.mappaint;
+
+import static org.openstreetmap.josm.tools.Utils.equal;
+import java.awt.Image;
+
+import javax.swing.GrayFilter;
+import javax.swing.ImageIcon;
+
+public class MapImage<I extends Image> {
+    /**
+     * ImageIcon can chage while the image is loading.
+     */
+    public I img;
+
+    public int alpha = 255;
+
+    /**
+     * The 4 following fields are only used to check for equality.
+     */
+    public String name;
+    public StyleSource source;
+    public int width = -1;
+    public int height = -1;
+
+    private Image disabledImg;
+
+    public MapImage(String name, StyleSource source) {
+        this.name = name;
+        this.source = source;
+    }
+
+    public Image getDisabled() {
+        if (disabledImg != null)
+            return disabledImg;
+        return disabledImg = GrayFilter.createDisabledImage(img);
+    }
+
+    // img changes when image is fully loaded and can't be used for equality check.
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null || getClass() != obj.getClass())
+            return false;
+        final MapImage other = (MapImage) obj;
+        return  alpha == other.alpha &&
+                equal(name, other.name) &&
+                equal(source, other.source) &&
+                width == other.width &&
+                height == other.height;
+    }
+
+    @Override
+    public int hashCode() {
+        int hash = 7;
+        hash = 67 * hash + alpha;
+        hash = 67 * hash + name.hashCode();
+        hash = 67 * hash + source.hashCode();
+        hash = 67 * hash + width;
+        hash = 67 * hash + height;
+        return hash;
+    }
+
+}