Changeset 8978 for trunk/psLib/src/imageops/psImageBackground.c

Timestamp:

Sep 25, 2006, 5:52:59 PM (20 years ago)

Author:

Paul Price

Message:

Subtract the median when we add the numbers, so we don't get numerical problems

File:

• trunk/psLib/src/imageops/psImageBackground.c (modified) (2 diffs)

trunk/psLib/src/imageops/psImageBackground.c

@@ -49 +49 @@
         int iy = pixel / nx;
 
-        if (mask && mask->data.U8[iy][ix] & maskValue) {
+        if (!isfinite(image->data.F32[iy][ix]) || (mask && mask->data.U8[iy][ix] & maskValue)) {
             continue;
         }
@@ -72 +72 @@
     }
 
+    // Subtract the median when we add the numbers, so we don't get numerical problems
+    float median = npts % 2 ? 0.5 * (values->data.F32[npts/2 - 1] + values->data.F32[npts/2]) :
+                   values->data.F32[npts/2];
     double value = 0;
     for (long i = imin; (i <= imax) && (i < n); i++) {
-        value += values->data.F32[i];
+        value += values->data.F32[i] - median;
     }
-    value = value / npts;
+    value = value / npts + median;
 
     stats->robustMedian = value;