[gegl] noise-simplex: deal with mipmap rendering

[Øyvind Kolås <ok src gnome org>]

commit 63b7636fa3c58d3e4bfe36afd22688b732471246
Author: Øyvind Kolås <pippin gimp org>
Date:   Fri Jul 4 19:39:26 2014 +0200

    noise-simplex: deal with mipmap rendering

 operations/common/noise-simplex.c |   51 +++++++++++++++++++++----------------
 1 files changed, 29 insertions(+), 22 deletions(-)
---
diff --git a/operations/common/noise-simplex.c b/operations/common/noise-simplex.c
index badb31f..5e394f0 100644
--- a/operations/common/noise-simplex.c
+++ b/operations/common/noise-simplex.c
@@ -227,32 +227,39 @@ c_process (GeglOperation       *operation,
            const GeglRectangle *roi,
            gint                 level)
 {
+  gint factor = 1 << level;
   GeglProperties *o = GEGL_PROPERTIES (operation);
   Context     context;
-  gfloat     *pixel;
-  gint        s, t;
+  gfloat     *pixel = out_buf;
 
-  context.seed = o->seed;
-
-  for (t = 0, pixel = out_buf ; t < roi->height ; t += 1)
-    {
-      for (s = 0 ; s < roi->width ; s += 1, pixel += 1)
-        {
-          gint    i;
-          gdouble c, d;
-
-          /* Pile up noise octaves onto the output value. */
+  gint x = roi->x;
+  gint y = roi->y;
 
-          for (i = 0, c = 1, d = o->scale / 50.0, *pixel = 0;
-               i < o->iterations;
-               c *= 2, d *= 2, i += 1)
-            {
-              *pixel += noise2 ((double) (s + roi->x) * d,
-                                (double) (t + roi->y) * d,
-                                &context) / c;
-            }
-        }
-    }
+  context.seed = o->seed;
+    
+  while (n_pixels --)
+  {
+    gint    i;
+    gdouble c, d;
+
+    /* Pile up noise octaves onto the output value. */
+
+    for (i = 0, c = 1, d = o->scale / 50.0, *pixel = 0;
+         i < o->iterations;
+         c *= 2, d *= 2, i += 1)
+      {
+        *pixel += noise2 ((double) (x) * d * factor, (double) (y) * d * factor, &context) / c;
+      }
+
+    pixel += 1;
+
+    x++;
+    if (x>=roi->x + roi->width)
+      {
+        x=roi->x;
+        y++;
+      }
+  }
 
   return TRUE;
 }