Index: /branches/czw_branch/20120906/psLib/src/imageops/psImagePixelManip.c
===================================================================
--- /branches/czw_branch/20120906/psLib/src/imageops/psImagePixelManip.c	(revision 34626)
+++ /branches/czw_branch/20120906/psLib/src/imageops/psImagePixelManip.c	(revision 34627)
@@ -234,4 +234,23 @@
       pixelsOverlaid += (imageRowLimit - y0) * (imageColLimit - x0);	\
     }
+
+#define psImageOverlayLoopMask(DATATYPE) {		    \
+      for (int row=y0;row<imageRowLimit;row++) {	    \
+	ps##DATATYPE* imageRow = image->data.DATATYPE[row];	   \
+	ps##DATATYPE* overlayRow = overlay->data.DATATYPE[row-y0]; \
+	for (int col=x0;col<imageColLimit;col++) {		   \
+	  if (!isfinite(imageRow[col])) {			   \
+	    imageRow[col] = overlayRow[col-x0];		   \
+	  }							   \
+	  else if (!isfinite(overlayRow[col-x0])) {		   \
+	    imageRow[col] = imageRow[col];			   \
+	  }							   \
+	  else {						   \
+	    imageRow[col] &= overlayRow[col-x0];		   \
+	  }								\
+	}								\
+      }									\
+      pixelsOverlaid += (imageRowLimit - y0) * (imageColLimit - x0);	\
+    }
 	
     
@@ -295,5 +314,5 @@
     case 'E': \
       psImageOverlayLoopClean(DATATYPE,=); \
-      break;			       \
+      break;				   \
     case '/': \
         psImageOverlayLoopDivide(DATATYPE,BADVALUE); \
@@ -309,14 +328,45 @@
     } \
     break;
+    #define psImageOverlayCaseInt(DATATYPE,BADVALUE) \
+case PS_TYPE_##DATATYPE: \
+    switch (*op) { \
+    case '+': \
+        psImageOverlayLoop(DATATYPE,+=); \
+        break; \
+    case '-': \
+        psImageOverlayLoop(DATATYPE,-=); \
+        break; \
+    case '*': \
+        psImageOverlayLoop(DATATYPE,*=); \
+        break; \
+    case 'E': \
+      psImageOverlayLoopClean(DATATYPE,=); \
+      break;				   \
+    case 'M':				   \
+      psImageOverlayLoopMask(DATATYPE);	   \
+      break;				   \
+    case '/': \
+        psImageOverlayLoopDivide(DATATYPE,BADVALUE); \
+        break; \
+    case '=': \
+        psImageOverlaySetLoop(DATATYPE);		\
+        break; \
+    default: \
+        psError(PS_ERR_BAD_PARAMETER_VALUE, true, \
+                _("Specified operation, '%s', is not supported."), \
+                op); \
+        return pixelsOverlaid; \
+    } \
+    break;
 
     switch (type) {
-        psImageOverlayCase(U8, 0);
-        psImageOverlayCase(U16,0);
-        psImageOverlayCase(U32,0);       // Not a requirement
-        psImageOverlayCase(U64,0);       // Not a requirement
-        psImageOverlayCase(S8, 0);
-        psImageOverlayCase(S16,0);
-        psImageOverlayCase(S32,0);       // Not a requirement
-        psImageOverlayCase(S64,0);       // Not a requirement
+        psImageOverlayCaseInt(U8, 0);
+        psImageOverlayCaseInt(U16,0);
+        psImageOverlayCaseInt(U32,0);       // Not a requirement
+        psImageOverlayCaseInt(U64,0);       // Not a requirement
+        psImageOverlayCaseInt(S8, 0);
+        psImageOverlayCaseInt(S16,0);
+        psImageOverlayCaseInt(S32,0);       // Not a requirement
+        psImageOverlayCaseInt(S64,0);       // Not a requirement
         psImageOverlayCase(F32,NAN);
         psImageOverlayCase(F64,NAN);