Fixed Bug 4258: Large image masks in Non-Rectangular trait lock up the GUI. Don't build opqaue Area by unioning one 1x1 Area per pixel; instead, construct opaque horizontal stripes. This makes performance tollerable without much effort. Doing this properly using an edge-finding algorithm on a background thread would be quite a lot more work.
Fixed Bug 4258: Large image masks in Non-Rectangular trait lock up the GUI.
Don't build opqaue Area by unioning one 1x1 Area per pixel; instead, construct opaque horizontal stripes. This makes performance tollerable without much effort. Doing this properly using an edge-finding algorithm on a background thread would be quite a lot more work.

git-svn-id: ae08250ad33602a4155ea07c044985523749a64a@8072 67b53d14-2c14-4ace-a08f-0dab2b34000c

rzymek/vassal-src,rzymek/vassal-src