add TextureAtlas loader helper class to handle json loading

src/com/blarg/gdx/graphics/atlas/TextureAtlasLoader.java

@@ -0,0 +1,33 @@
+package com.blarg.gdx.graphics.atlas;
+
+import com.badlogic.gdx.Gdx;
+import com.badlogic.gdx.files.FileHandle;
+import com.badlogic.gdx.graphics.Texture;
+import com.badlogic.gdx.utils.Json;
+
+public final class TextureAtlasLoader {
+	public static TextureAtlas load(FileHandle configFile) {
+		Json json = new Json();
+		JsonTextureAtlasDefinition config = json.fromJson(JsonTextureAtlasDefinition.class, configFile);
+
+		if (config.texture == null)
+			throw new RuntimeException("No texture specified.");
+		if (config.tiles == null || config.tiles.size() == 0)
+			throw new RuntimeException("No tiles defined.");
+
+		// TODO: loading via AssetManager
+		Texture texture = new Texture(Gdx.files.internal(config.texture));
+		CustomGridTextureAtlas atlas = new CustomGridTextureAtlas(texture);
+
+		for (int i = 0; i < config.tiles.size(); ++i) {
+			JsonTextureAtlasTile tile = config.tiles.get(i);
+			// TODO: parameter value error checking
+			if (tile.autogrid)
+				atlas.addGrid(tile.x, tile.y, tile.tileWidth, tile.tileHeight, tile.numTilesX, tile.numTilesY, tile.border);
+			else
+				atlas.add(tile.x, tile.y, tile.width, tile.height);
+		}
+
+		return atlas;
+	}
+}