[gegl] Fix opencl constrast-curve operation

[Øyvind Kolås <ok src gnome org>]

commit dda2a7d50460b3c3a2c21499760446fbedd7eb81
Author: André Tupinambá <andrelrt gmail com>
Date:   Sun Sep 20 10:46:37 2015 -0300

    Fix opencl constrast-curve operation

 opencl/contrast-curve.cl   |   13 ++++---------
 opencl/contrast-curve.cl.h |   13 ++++---------
 2 files changed, 8 insertions(+), 18 deletions(-)
---
diff --git a/opencl/contrast-curve.cl b/opencl/contrast-curve.cl
index 4abf13e..15f816c 100644
--- a/opencl/contrast-curve.cl
+++ b/opencl/contrast-curve.cl
@@ -23,16 +23,11 @@ __kernel void cl_contrast_curve(__global const float2 *in,
 {
   int gid     = get_global_id(0);
   float2 in_v = in[gid];
-  int x       = in_v.x * num_sampling_points;
-  float y;
 
-  if(x < 0)
-    y = curve[0];
-  else if (x < num_sampling_points)
-    y = curve[x];
-  else
-    y = curve[num_sampling_points - 1];
+  int idx = (int) fmin(num_sampling_points - 1,
+                       fmax(0f,
+                            in_v.x * num_sampling_points));
 
-  out[gid] = (float2) (y, in_v.y);
+  out[gid] = (float2) (curve[idx], in_v.y);
 }
 
diff --git a/opencl/contrast-curve.cl.h b/opencl/contrast-curve.cl.h
index 7912cd7..a6903c7 100644
--- a/opencl/contrast-curve.cl.h
+++ b/opencl/contrast-curve.cl.h
@@ -24,16 +24,11 @@ static const char* contrast_curve_cl_source =
 "{                                                                             \n"
 "  int gid     = get_global_id(0);                                             \n"
 "  float2 in_v = in[gid];                                                      \n"
-"  int x       = in_v.x * num_sampling_points;                                 \n"
-"  float y;                                                                    \n"
 "                                                                              \n"
-"  if(x < 0)                                                                   \n"
-"    y = curve[0];                                                             \n"
-"  else if (x < num_sampling_points)                                           \n"
-"    y = curve[x];                                                             \n"
-"  else                                                                        \n"
-"    y = curve[num_sampling_points - 1];                                       \n"
+"  int idx = (int) fmin(num_sampling_points - 1,                               \n"
+"                       fmax(0f,                                               \n"
+"                            in_v.x * num_sampling_points));                   \n"
 "                                                                              \n"
-"  out[gid] = (float2) (y, in_v.y);                                            \n"
+"  out[gid] = (float2) (curve[idx], in_v.y);                                   \n"
 "}                                                                             \n"
 ;