Index: trunk/psModules/src/objects/pmSource.c
===================================================================
--- trunk/psModules/src/objects/pmSource.c	(revision 27531)
+++ trunk/psModules/src/objects/pmSource.c	(revision 27657)
@@ -180,4 +180,5 @@
     source->type = in->type;
     source->mode = in->mode;
+    source->imageID = in->imageID;
 
     return(source);
@@ -1058,4 +1059,19 @@
     psF32 fA = (A->peak == NULL) ? 0 : A->peak->y;
     psF32 fB = (B->peak == NULL) ? 0 : B->peak->y;
+
+    psF32 diff = fA - fB;
+    if (diff > FLT_EPSILON) return (+1);
+    if (diff < FLT_EPSILON) return (-1);
+    return (0);
+}
+
+// sort by X (ascending)
+int pmSourceSortByX (const void **a, const void **b)
+{
+    pmSource *A = *(pmSource **)a;
+    pmSource *B = *(pmSource **)b;
+
+    psF32 fA = (A->peak == NULL) ? 0 : A->peak->x;
+    psF32 fB = (B->peak == NULL) ? 0 : B->peak->x;
 
     psF32 diff = fA - fB;