second place of the same bug

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

@@ -13108,7 +13108,7 @@ public class QuadCLTCPU {
 		  if (debugLevel > -1) {
 			  System.out.println("backdropPixels = "+backdropPixels+" h_margin = "+h_margin+" v_margin = "+v_margin);
 		  }
-		  int [] src_pixels = (int []) imp.getProcessor().getPixels();
+		  int [] src_pixels = (int []) imp.getProcessor().convertToColorProcessor().getPixels();
 		  int [] pixels = new int [width2* height2];
 		  int black = noalpha ? 0 :        0xff000000;
 		  int mask =  noalpha ? 0xffffff : 0xffffffff;