Working on occluded BG. Some works

src/main/java/com/elphel/imagej/gpu/TpTask.java

@@ -176,6 +176,10 @@ public class TpTask {
 	public int getTileX(){
 		return tx;
 	}
+	public int [] getTileXY(){
+		return new int [] {tx,ty};
+	}
+	
 	public int getTask() {
 		return task;
 	}

src/main/java/com/elphel/imagej/tileprocessor/QuadCLT.java

@@ -1792,6 +1792,7 @@ public class QuadCLT extends QuadCLTCPU {
 			final int          discard_frame_edges, // do not use tiles that have pixels closer to the frame margins 
 			final int          keep_frame_tiles, // do not discard pixels for border tiles in reference frame 
 			final boolean      keep_channels,
+			final TpTask[][][] tp_tasks_ret, // if not null, should be [1] - will return tp_tasks_ret[0] = tp_tasks
 			final int          debugLevel){
 		// FIXME: Move to clt_parameters;
 		final double max_overlap =    0.6; 
@@ -1899,11 +1900,12 @@ public class QuadCLT extends QuadCLTCPU {
 		if (tp_tasks[0].length == 0) {
 			if (debugLevel > -1) {
 				System.out.println("texturesGPUFromDSI(): no tiles to process");
-				
 			}
 			return null;
 		}
-		
+		if (tp_tasks_ret != null) {
+			tp_tasks_ret[0] = tp_tasks; // return tp_tasks to caller
+		}
 		///		scene.saveQuadClt(); // to re-load new set of Bayer images to the GPU (do nothing for CPU) and Geometry
 		ImageDtt image_dtt = new ImageDtt(
 				scene.getNumSensors(),