[gegl] noise-reduction: fix math of 2nd order derivative criteria

[Ãyvind KolÃs <ok src gnome org>]

commit ba9d2821176ecc67a674f212105f6b87aaf7e0c5
Author: Ãyvind KolÃs <pippin gimp org>
Date:   Wed Jun 15 11:32:54 2011 +0100

    noise-reduction: fix math of 2nd order derivative criteria
    
    The math was wrong, this change is mostly cosmetic since the result does not
    change at all.

 operations/common/noise-reduction.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)
---
diff --git a/operations/common/noise-reduction.c b/operations/common/noise-reduction.c
index 9357541..ef4fdd7 100644
--- a/operations/common/noise-reduction.c
+++ b/operations/common/noise-reduction.c
@@ -18,7 +18,7 @@
 
 #ifdef GEGL_CHANT_PROPERTIES
 
-gegl_chant_int    (iterations,        "Iterations", 1,   50, 5,     "Number of iterations, more iterations takes longer time but might also make the image less noisy.")
+gegl_chant_int (iterations, "Iterations", 1, 50, 5, "Number of iterations, more iterations takes longer time but might also make the image less noisy.")
 
 #else
 
@@ -147,8 +147,7 @@ noise_reduction (GeglBuffer          *src,
                 {  /* initialize original gradients */
                   float *cpix  = center_pix + offsets[dir];
                   float *cpixb = center_pix + offsets[SYMMETRY_PIXEL(dir)];
-                  original_gradient[dir] = POW2(center_pix[c] - cpix[c]) +
-                                           POW2(center_pix[c] - cpixb[c]);
+                  original_gradient[dir] = POW2((center_pix[c] - cpix[c]) + (center_pix[c] - cpixb[c]));
                 }
 
               /* try smearing in data from each of the 8 neighbours */
@@ -164,7 +163,7 @@ noise_reduction (GeglBuffer          *src,
                       {
                         float *cpix  = center_pix + offsets[comparison_dir];
                         float *cpixb = center_pix + offsets[SYMMETRY_PIXEL(comparison_dir)];
-                        float  new_gradient = POW2(result - cpix[c]) + POW2(result - cpixb[c]);
+                        float  new_gradient = POW2((result - cpix[c]) + (result - cpixb[c]));
 
                         if (G_UNLIKELY (new_gradient > original_gradient[comparison_dir]))
                           { /* The 2nd order derivative increased, use original value instead */
@@ -196,7 +195,7 @@ noise_reduction (GeglBuffer          *src,
                       {
                         float *cpix  = center_pix + offsets[comparison_dir];
                         float *cpixb = center_pix + offsets[SYMMETRY_PIXEL(comparison_dir)];
-                        float  new_gradient = POW2(result - cpix[c]) + POW2(result - cpixb[c]);
+                        float  new_gradient = POW2((result - cpix[c]) + (result - cpixb[c]));
 
                         if (G_UNLIKELY (new_gradient > original_gradient[comparison_dir]))
                           { /* The 2nd order derivative increased, use original value instead */