diff --git a/panda/src/pnmimage/pnmImage.cxx b/panda/src/pnmimage/pnmImage.cxx
index 465e11dc83..76a9747031 100644
--- a/panda/src/pnmimage/pnmImage.cxx
+++ b/panda/src/pnmimage/pnmImage.cxx
@@ -1159,6 +1159,41 @@ threshold(const PNMImage &select_image, int channel, double threshold,
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: PNMImage::rescale
+//       Access: Published
+//  Description: Rescales the RGB channel values so that any values in
+//               the original image between min_val and max_val are
+//               expanded to the range 0 .. 1.  Values below min_val
+//               are set to 0, and values above max_val are set to 1.
+//               Does not affect the alpha channel, if any.
+////////////////////////////////////////////////////////////////////
+void PNMImage::
+rescale(double min_val, double max_val) {
+  double scale = max_val - min_val;
+
+  if (_num_channels <= 2) {
+    // Grayscale.
+    for (int y = 0; y < get_y_size(); y++) {
+      for (int x = 0; x < get_x_size(); x++) {
+        double val = get_gray(x, y);
+        set_gray(x, y, (val - min_val) / scale);
+      }
+    }
+  } else {
+    // RGB(A).
+    for (int y = 0; y < get_y_size(); y++) {
+      for (int x = 0; x < get_x_size(); x++) {
+        LRGBColord xel = get_xel(x, y);
+        set_xel(x, y, 
+                (xel[0] - min_val) / scale,
+                (xel[1] - min_val) / scale,
+                (xel[2] - min_val) / scale);
+      }
+    }
+  }
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: PNMImage::copy_channel
 //       Access: Published
diff --git a/panda/src/pnmimage/pnmImage.h b/panda/src/pnmimage/pnmImage.h
index 33822a7261..166b3e3dc0 100644
--- a/panda/src/pnmimage/pnmImage.h
+++ b/panda/src/pnmimage/pnmImage.h
@@ -214,6 +214,8 @@ PUBLISHED:
   void threshold(const PNMImage &select_image, int channel, double threshold,
                  const PNMImage &lt, const PNMImage &ge);
 
+  void rescale(double min_val, double max_val);
+
   void copy_channel(const PNMImage &copy, int xto, int yto, int cto,
                     int xfrom = 0, int yfrom = 0, int cfrom = 0,
                     int x_size = -1, int y_size = -1);