Index: trunk/psphot/src/psphotModelBackground.c
===================================================================
--- trunk/psphot/src/psphotModelBackground.c	(revision 32348)
+++ trunk/psphot/src/psphotModelBackground.c	(revision 33963)
@@ -37,10 +37,11 @@
 // corresponding to the model.  Other information about the background model is saved on the
 // readout->analysis
-static bool psphotModelBackgroundReadout(psImage *model,  // Model image
-                                  psImage *modelStdev, // Model stdev image
-                                  psMetadata *analysis, // Analysis metadata for outputs
-                                  pmReadout *readout, // Readout for which to generate a background model
-                                  psImageBinning *binning, // Binning parameters
-                                  const pmConfig *config // Configuration
+bool psphotModelBackgroundReadout(psImage *model,  // Model image
+				  psImage *modelStdev, // Model stdev image
+				  psMetadata *analysis, // Analysis metadata for outputs
+				  pmReadout *readout, // Readout for which to generate a background model
+				  psImageBinning *binning, // Binning parameters
+				  const pmConfig *config,// Configuration
+				  bool useVarianceImage
     )
 {
@@ -49,5 +50,6 @@
     bool status = true;
 
-    psImage *image = readout->image, *mask = readout->mask; // Image and mask for readout
+    psImage *image = useVarianceImage ? readout->variance : readout->image;
+    psImage *mask = readout->mask; // Image and mask for readout
 
     // select the appropriate recipe information
@@ -143,5 +145,7 @@
 
     // we save the binning structure for use in psphotMagnitudes
-    psMetadataAddPtr(analysis, PS_LIST_TAIL, "PSPHOT.BACKGROUND.BINNING", PS_DATA_UNKNOWN | PS_META_REPLACE, "Background binning", binning);
+    if (!useVarianceImage) {
+	psMetadataAddPtr(analysis, PS_LIST_TAIL, "PSPHOT.BACKGROUND.BINNING", PS_DATA_UNKNOWN | PS_META_REPLACE, "Background binning", binning);
+    }
 
     psVector *dQ = psVectorAllocEmpty (100, PS_TYPE_F32);
@@ -159,6 +163,6 @@
 
     // measure clipped median for subimages
-    psRegion ruffRegion = {0,0,0,0};
-    psRegion fineRegion = {0,0,0,0};
+    psRegion ruffRegion = psRegionSet (0,0,0,0);
+    psRegion fineRegion = psRegionSet (0,0,0,0);
     for (int iy = 0; iy < model->numRows; iy++) {
         for (int ix = 0; ix < model->numCols; ix++) {
@@ -330,25 +334,30 @@
     psVectorStats (statsDQ, dQ, NULL, NULL, 0);
 
-    psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_MEAN",  PS_META_REPLACE, "sky mean", Value);
-    psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_STDEV", PS_META_REPLACE, "sky stdev", ValueStdev);
-    psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_DQ",    PS_META_REPLACE, "sky quartile slope", statsDQ->sampleMedian);
-    psLogMsg ("psphot", PS_LOG_INFO, "image sky : mean %f, stdev %f, dQ %f", Value, ValueStdev, statsDQ->sampleMedian);
-
-    // measure image and background stats and save for later output
-    psStats *statsBck = psStatsAlloc (PS_STAT_SAMPLE_MEAN |
-                                      PS_STAT_SAMPLE_STDEV |
-                                      PS_STAT_MIN |
-                                      PS_STAT_MAX);
-    psImageStats (statsBck, model, NULL, 0);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MN",  PS_META_REPLACE, "sky model mean",          statsBck->sampleMean);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_SIG", PS_META_REPLACE, "sky model stdev",         statsBck->sampleStdev);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_DEV", PS_META_REPLACE, "sky stdev",               ValueStdev);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_DQ",  PS_META_REPLACE, "sky quartile slope",      statsDQ->sampleMedian);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MAX", PS_META_REPLACE, "sky model maximum value", statsBck->max);
-    psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MIN", PS_META_REPLACE, "sky model minimum value", statsBck->min);
-    psMetadataAddS32 (readout->analysis, PS_LIST_TAIL, "MSKY_NX", PS_META_REPLACE, "sky model size (x)",      model->numCols);
-    psMetadataAddS32 (readout->analysis, PS_LIST_TAIL, "MSKY_NY", PS_META_REPLACE, "sky model size (y)",      model->numRows);
-    psLogMsg ("psphot", PS_LOG_INFO, "background sky : min %f mean %f max %f stdev %f",
-              statsBck->min, statsBck->sampleMean, statsBck->max, statsBck->sampleStdev);
+    if (!useVarianceImage) {
+	psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_MEAN",  PS_META_REPLACE, "sky mean", Value);
+	psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_STDEV", PS_META_REPLACE, "sky stdev", ValueStdev);
+	psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "SKY_DQ",    PS_META_REPLACE, "sky quartile slope", statsDQ->sampleMedian);
+	psLogMsg ("psphot", PS_LOG_INFO, "image sky : mean %f, stdev %f, dQ %f", Value, ValueStdev, statsDQ->sampleMedian);
+
+	// measure image and background stats and save for later output
+	psStats *statsBck = psStatsAlloc (PS_STAT_SAMPLE_MEAN |
+					  PS_STAT_SAMPLE_STDEV |
+					  PS_STAT_MIN |
+					  PS_STAT_MAX);
+	psImageStats (statsBck, model, NULL, 0);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MN",  PS_META_REPLACE, "sky model mean",          statsBck->sampleMean);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_SIG", PS_META_REPLACE, "sky model stdev",         statsBck->sampleStdev);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_DEV", PS_META_REPLACE, "sky stdev",               ValueStdev);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_DQ",  PS_META_REPLACE, "sky quartile slope",      statsDQ->sampleMedian);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MAX", PS_META_REPLACE, "sky model maximum value", statsBck->max);
+	psMetadataAddF32 (readout->analysis, PS_LIST_TAIL, "MSKY_MIN", PS_META_REPLACE, "sky model minimum value", statsBck->min);
+	psMetadataAddS32 (readout->analysis, PS_LIST_TAIL, "MSKY_NX", PS_META_REPLACE, "sky model size (x)",      model->numCols);
+	psMetadataAddS32 (readout->analysis, PS_LIST_TAIL, "MSKY_NY", PS_META_REPLACE, "sky model size (y)",      model->numRows);
+	psLogMsg ("psphot", PS_LOG_INFO, "background sky : min %f mean %f max %f stdev %f",
+		  statsBck->min, statsBck->sampleMean, statsBck->max, statsBck->sampleStdev);
+	psFree(statsBck);
+    } else {
+	psLogMsg ("psphot", PS_LOG_INFO, "variance data : mean %f, stdev %f, dQ %f", Value, ValueStdev, statsDQ->sampleMedian);
+    }
 
     psFree(statsDQ);
@@ -356,5 +365,4 @@
 
     psFree(stats);
-    psFree(statsBck);
     psFree(statsDefaults);
     psFree(binning);
@@ -375,5 +383,5 @@
     psImage *modelStdev = psImageAlloc(binning->nXruff, binning->nYruff, PS_TYPE_F32); // Standard deviation
 
-    if (!psphotModelBackgroundReadout(model, modelStdev, readout->analysis, readout, binning, config)) {
+    if (!psphotModelBackgroundReadout(model, modelStdev, readout->analysis, readout, binning, config, false)) {
         psFree(model);
         psFree(modelStdev);
@@ -400,5 +408,5 @@
     pmReadout *modelStdev = pmFPAGenerateReadout(config, view, "PSPHOT.BACKMDL.STDEV", inFPA, binning, index);
 
-    if (!psphotModelBackgroundReadout(model->image, modelStdev->image, model->analysis, readout, binning, config)) {
+    if (!psphotModelBackgroundReadout(model->image, modelStdev->image, model->analysis, readout, binning, config, false)) {
         psError(PS_ERR_UNKNOWN, false, "Unable to generate background model");
         return false;