[gegl/soc-2012-ops: 23/29] Wind Operation

[Maxime Nicco <maxnicco src gnome org>]

commit 502f01f2611461bb90b2fc2dd87870263f4df7f2
Author: Hans Lo <hansshulo gmail com>
Date:   Wed Jul 25 05:43:13 2012 -0400

    Wind Operation
    
    Currently every edge that can bleed bleeds. There needs to be some
    randomization.

 operations/common/wind.c |  208 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 208 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/wind.c b/operations/common/wind.c
new file mode 100644
index 0000000..8bb5a98
--- /dev/null
+++ b/operations/common/wind.c
@@ -0,0 +1,208 @@
+/* This file is an image processing operation for GEGL
+ *
+ * GEGL is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * GEGL is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with GEGL; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright Nigel Wetten
+ * Copyright 2000 Tim Copperfield <timecop japan co jp>
+ * Copyright 2011 Hans Lo <hansshulo gmail com>
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+
+#ifdef GEGL_CHANT_PROPERTIES
+
+gegl_chant_double (threshold, _("Threshold"), 0.0, 1.0, 0.2,
+                   _("Higher values restrict the effect to fewer "
+                     "areas of the image"))
+
+gegl_chant_int (strength, _("Strength"), 1, 100, 4,
+                _("Higher values increase the magnitude of the effect"))
+
+#else
+
+#define GEGL_CHANT_TYPE_AREA_FILTER
+#define GEGL_CHANT_C_FILE       "wind.c"
+
+#include "gegl-chant.h"
+//#include <math.h>
+#include <stdlib.h>
+
+
+//assume leading
+//assume has alpha
+static void
+get_derivative (gfloat   *pixel1,
+                gfloat   *pixel2,
+                gfloat   *derivative)
+{
+  gint i;
+  for (i = 0; i < 4; i++)
+    derivative[i] = pixel1[i] - pixel2[i];
+}
+
+static gboolean
+threshold_exceeded (gfloat  *pixel1,
+                    gfloat  *pixel2,
+                    gfloat   threshold)
+{
+  gfloat derivative[4];
+  gint i;
+  gfloat sum;
+
+  get_derivative (pixel1, pixel2, derivative);
+
+  sum = 0;
+  for (i = 0; i < 4; i++)
+    sum += derivative[i];
+
+  return ((sum / 4.0) > threshold);
+}
+
+static void prepare (GeglOperation *operation)
+{
+  GeglChantO              *o;
+  GeglOperationAreaFilter *op_area;
+
+  op_area = GEGL_OPERATION_AREA_FILTER (operation);
+  o       = GEGL_CHANT_PROPERTIES (operation);
+
+  op_area->left   = o->strength; //only from left for now
+
+  gegl_operation_set_format (operation, "input",
+                             babl_format ("RGBA float"));
+  gegl_operation_set_format (operation, "output",
+                             babl_format ("RGBA float"));
+}
+
+static gboolean
+process (GeglOperation       *operation,
+         GeglBuffer          *input,
+         GeglBuffer          *output,
+         const GeglRectangle *result,
+         gint                 level)
+{
+  GeglChantO *o                    = GEGL_CHANT_PROPERTIES (operation);
+  GeglOperationAreaFilter *op_area = GEGL_OPERATION_AREA_FILTER (operation);
+
+  gfloat *src_buf;
+  gfloat *dst_buf;
+
+  gint n_pixels = result->width * result->height;
+  GeglRectangle src_rect;
+
+  gfloat *blend_pix; //left edge
+  gfloat *target_pix; //normally right edge
+  gfloat *base_pix; //input pixel corresponding to write
+  gfloat *dst_pix; //write target
+
+  gint x, y;
+  gint total_pixels;
+
+  gfloat denominator;
+
+  gint n;
+  gint bleed_length_max;
+  gint bleed_length;
+
+  /* code to calculate each left edge and the associated bleed length
+   that is randomly generated*/
+
+  src_rect.x      = result->x - op_area->left;
+  src_rect.width  = result->width + op_area->left + op_area->right;
+  src_rect.y      = result->y - op_area->top;
+  src_rect.height = result->height + op_area->top + op_area->bottom;
+
+  total_pixels = src_rect.width * src_rect.height;
+
+  src_buf = g_slice_alloc (4 * total_pixels * sizeof (gfloat));
+  dst_buf = g_slice_alloc (4 * total_pixels * sizeof (gfloat));
+
+  gegl_buffer_get (input, &src_rect, 1.0, babl_format ("RGBA float"),
+                   src_buf, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_NONE);
+
+  //for each pixel
+  base_pix = src_buf + 4 * o->strength;
+  dst_pix = dst_buf;
+  x = 0;
+  y = 0;
+  n_pixels = result->width * result->height;
+  bleed_length = o->strength;
+  while (n_pixels--)
+    {
+      /* need to check up to the max bleed length to see if there is a left edge
+       which bleeds to the current pixel and bleed approriately */
+
+      gint i;
+      denominator = 1.0/(gfloat) bleed_length;;
+      for (i = 0; i < 4; i++)
+            dst_pix[i] = base_pix[i];
+      for (n = 0; n < bleed_length; n++)
+        {
+          target_pix = base_pix - 4 * n;
+          blend_pix = target_pix - 4 * 3;
+          if (x < 3 + n)
+            continue;
+
+          if (threshold_exceeded (blend_pix, target_pix, o->threshold))
+            {
+              gfloat blend_color[4];
+              gfloat blend_amount[4];
+              for (i = 0; i < 4; i++)
+                {
+                  blend_color[i] = blend_pix[i];
+                  blend_amount[i] = target_pix[i] - blend_pix[i];
+                  blend_color[i] += blend_amount[i] * (gfloat) n * denominator;
+                  dst_pix[i] = (2.0 * blend_color[i] + dst_pix[i])/3.0;
+                }
+            }
+        }
+      dst_pix += 4;
+      /* update x and y coordinates */
+      x++;
+      base_pix += 4;
+      if (x >= result->width)
+        {
+          x = 0;
+          y++;
+          base_pix += 4 * o->strength;
+        }
+    }
+  gegl_buffer_set (output, result, 0,
+                   babl_format ("RGBA float"),
+                   dst_buf, GEGL_AUTO_ROWSTRIDE);
+  g_slice_free1 (4 * total_pixels * sizeof (gfloat), src_buf);
+  g_slice_free1 (4 * total_pixels * sizeof (gfloat), dst_buf);
+  return TRUE;
+}
+
+static void
+gegl_chant_class_init (GeglChantClass *klass)
+{
+  GeglOperationClass       *operation_class;
+  GeglOperationFilterClass *filter_class;
+
+  operation_class = GEGL_OPERATION_CLASS (klass);
+  filter_class    = GEGL_OPERATION_FILTER_CLASS (klass);
+
+  filter_class->process    = process;
+  operation_class->prepare = prepare;
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "categories" , "distort",
+                                 "name"       , "gegl:wind",
+                                 "description", _("Wind-like bleed effect"),
+                                 NULL);
+}
+#endif