[babl] Use absolute error instead of average error for path check

[Daniel Sabo <daniels src gnome org>]

commit 56be40fbef61fd32672209d38a5e874fea603e82
Author: Daniel Sabo <DanielSabo gmail com>
Date:   Sat Jan 11 18:44:32 2014 -0800

    Use absolute error instead of average error for path check

 babl/babl-fish-path.c |    6 +++---
 babl/babl-util.c      |   25 ++++++++++++++++++++++---
 babl/babl-util.h      |   11 ++++++++---
 3 files changed, 33 insertions(+), 9 deletions(-)
---
diff --git a/babl/babl-fish-path.c b/babl/babl-fish-path.c
index ebf2cb5..82838e9 100644
--- a/babl/babl-fish-path.c
+++ b/babl/babl-fish-path.c
@@ -708,9 +708,9 @@ get_path_instrumentation (FishPathInstrumentation *fpi,
   babl_process (fpi->fish_destination_to_rgba,
                 fpi->destination, fpi->destination_rgba_double, NUM_TEST_PIXELS);
 
-  *path_error = babl_rel_avg_error (fpi->destination_rgba_double,
-                                    fpi->ref_destination_rgba_double,
-                                    NUM_TEST_PIXELS * 4);
+  *path_error = babl_abs_error (fpi->destination_rgba_double,
+                                fpi->ref_destination_rgba_double,
+                                NUM_TEST_PIXELS * 4);
 
 #if 0
   fpi->fish_rgba_to_source->fish.processings--;
diff --git a/babl/babl-util.c b/babl/babl-util.c
index 92977ac..f99b54b 100644
--- a/babl/babl-util.c
+++ b/babl/babl-util.c
@@ -88,9 +88,28 @@ babl_process_cost (long ticks_start,
 }
 
 double
-babl_rel_avg_error (double *imgA,
-                    double *imgB,
-                    long    samples)
+babl_abs_error (const double *imgA,
+                const double *imgB,
+                long          samples)
+{
+  double abs_error = 0.0;
+  long   i;
+
+  for (i = 0; i < samples; i++)
+    {
+      double sample_error = fabs (imgA[i] - imgB[i]);
+
+      if (sample_error > abs_error)
+        abs_error = sample_error;
+    }
+
+  return abs_error;
+}
+
+double
+babl_rel_avg_error (const double *imgA,
+                    const double *imgB,
+                    long          samples)
 {
   double error = 0.0;
   long   i;
diff --git a/babl/babl-util.h b/babl/babl-util.h
index bdaeec8..8c49619 100644
--- a/babl/babl-util.h
+++ b/babl/babl-util.h
@@ -27,7 +27,12 @@ babl_process_cost (long ticks_start,
                    long ticks_end);
 
 double
-babl_rel_avg_error (double *imgA,
-                    double *imgB,
-                    long    samples);
+babl_rel_avg_error (const double *imgA,
+                    const double *imgB,
+                    long          samples);
+
+double
+babl_abs_error     (const double *imgA,
+                    const double *imgB,
+                    long          samples);
 #endif