Index: trunk/psphot/src/psphotSourceSize.c
===================================================================
--- trunk/psphot/src/psphotSourceSize.c	(revision 17113)
+++ trunk/psphot/src/psphotSourceSize.c	(revision 17396)
@@ -1,4 +1,6 @@
 # include "psphotInternal.h"
 # include <gsl/gsl_sf_gamma.h>
+
+float psphotModelContour (psImage *image, psImage *weight, psImage *mask, pmModel *model, float Ro);
 
 // we need to call this function after sources have been fitted to the PSF model and
@@ -14,5 +16,8 @@
     psTimerStart ("psphot");
 
-    float CR_NSIGMA_LIMIT = psMetadataLookupF32 (&status, recipe, "PSPHOT.CRNSIGMA.LIMIT");
+    float CR_NSIGMA_LIMIT = psMetadataLookupF32 (&status, recipe, "PSPHOT.CR.NSIGMA.LIMIT");
+    assert (status);
+
+    float EXT_NSIGMA_LIMIT = psMetadataLookupF32 (&status, recipe, "PSPHOT.EXT.NSIGMA.LIMIT");
     assert (status);
 
@@ -24,20 +29,24 @@
 	if (isfinite(source->crNsigma)) continue;
 
-	source->crNsigma  = -1.0;
-	source->extNsigma = -1.0;
-
 	// source must have been subtracted
-	source->crNsigma  = -3.0;
 	if (!(source->mode & PM_SOURCE_MODE_SUBTRACTED)) continue;
 
-	psF32 **resid = source->pixels->data.F32;
+	psF32 **resid  = source->pixels->data.F32;
 	psF32 **weight = source->weight->data.F32;
-	psU8 **mask = source->maskObj->data.U8;
+	psU8 **mask    = source->maskObj->data.U8;
+
+	// check for extendedness: measure the delta flux significance at the 1 sigma contour
+	source->extNsigma = psphotModelContour (source->pixels, source->weight, source->maskObj, source->modelPSF, 1.0);
+
+	// XXX prevent a source from being both CR and EXT?
+	if (source->extNsigma > EXT_NSIGMA_LIMIT) {
+	  source->mode |= PM_SOURCE_MODE_EXT_LIMIT;
+	}
 
 	int xPeak = source->peak->xf - source->pixels->col0 + 0.5;
 	int yPeak = source->peak->yf - source->pixels->row0 + 0.5;
 
-	// skip sources which are too close to a boundary
-	source->crNsigma  = -4.0;
+	// XXX for now, skip sources which are too close to a boundary
+	// XXX raise a flag?
 	if (xPeak < 1) continue;
 	if (xPeak > source->pixels->numCols - 2) continue;
@@ -46,5 +55,5 @@
 
 	// XXX for now, just skip any sources with masked pixels
-	source->crNsigma  = -5.0;
+	// XXX raise a flag?
 	bool keep = true;
 	for (int iy = -1; (iy <= +1) && keep; iy++) {
@@ -113,5 +122,4 @@
 	}
 	source->crNsigma  = (nCR > 0)  ? fCR / nCR : 0.0;
-	source->extNsigma = (nEXT > 0) ? fabs(fEXT) / nEXT : 0.0;
 	// NOTE: abs needed to make the Nsigma value positive 
 
@@ -122,5 +130,5 @@
 
 	if (source->crNsigma > CR_NSIGMA_LIMIT) {
-	  source->mode |= PM_SOURCE_MODE_CRLIMIT;
+	  source->mode |= PM_SOURCE_MODE_CR_LIMIT;
 	}
     }
@@ -169,2 +177,65 @@
  */
 
+
+// given the PSF ellipse parameters, navigate around the 1sigma contour, return the total
+// deviation in sigmas.  This is measure on the residual image - should we ignore negative
+// deviations?
+float psphotModelContour (psImage *image, psImage *weight, psImage *mask, pmModel *model, float Ro) {
+
+    psF32 *PAR = model->params->data.F32;
+
+    // Ro = (x / SXX)^2 + (y / SYY)^2 + x y SXY;
+    // y^2 (1/SYY^2) + y (x SXY) + (x / SXX)^2 - Ro = 0;
+    // y = [-(x SXY) +/- sqrt ((x SXY)^2 - 4 (1/SYY^2) ((x/SXX)^2 - Ro))] * [SYY^2 / 2];
+    // y = [-B +/- sqrt (B^2 - 4 A C)] / [2 A];
+
+    // min/max value of x is where T -> 0
+    // solve this for x2:
+    float Q = Ro * PS_SQR(PAR[PM_PAR_SXX]) / (1.0 - PS_SQR(PAR[PM_PAR_SXX]*PAR[PM_PAR_SYY]*PAR[PM_PAR_SXY]) / 4.0);
+    if (Q < 0.0) return NAN; // ellipse is imaginary
+
+    int xMax = sqrt(Q);
+    int xMin = -1.0*xMax;
+
+    int nPts = 0;
+    float nSigma = 0.0;
+
+    for (int x = xMin; x <= xMax; x++) {
+	float A = PS_SQR (1.0 / PAR[PM_PAR_SYY]);
+	float B = x * PAR[PM_PAR_SXY];
+	float C = PS_SQR (x / PAR[PM_PAR_SXX]) - Ro;
+
+	float T = PS_SQR(B) - 4*A*C;
+	if (T < 0.0) continue;
+    
+	float yP = (-B + sqrt (T)) / (2.0 * A);
+	float yM = (-B - sqrt (T)) / (2.0 * A);
+
+	int xPix  = x  + PAR[PM_PAR_XPOS] - image->col0 + 0.5;
+	int yPixM = yM + PAR[PM_PAR_YPOS] - image->row0 + 0.5;
+	int yPixP = yP + PAR[PM_PAR_YPOS] - image->row0 + 0.5;
+
+	if (xPix < 0) continue;
+	if (xPix >= image->numCols) continue;
+
+	if ((yPixM >= 0) && (yPixM < image->numRows)) {
+	    if (!mask || !mask->data.U8[yPixM][xPix]) {
+		float dSigma = image->data.F32[yPixM][xPix] / sqrt (weight->data.F32[yPixM][xPix]);
+		nSigma += dSigma;
+		nPts ++;
+	    }
+	}
+	
+	if (yPixM == yPixP) continue;
+
+	if ((yPixP >= 0) && (yPixP < image->numRows)) {
+	    if (!mask || !mask->data.U8[yPixP][xPix]) {
+		float dSigma = image->data.F32[yPixP][xPix] / sqrt (weight->data.F32[yPixP][xPix]);
+		nSigma += dSigma;
+		nPts ++;
+	    }
+	}
+    }	
+    nSigma /= nPts;
+    return nSigma;
+}