[gegl] added linear motion blur filter

[Øyvind Kolås <ok src gnome org>]

commit a49e0c356737578e0c1adccc06c20fc8642e195a
Author: Andy Gill <andyggill gmail com>
Date:   Sat Jan 29 18:58:47 2011 +0000

    added linear motion blur filter

 operations/common/motion-blur.c |  174 +++++++++++++++++++++++++++++++++++++++
 1 files changed, 174 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/motion-blur.c b/operations/common/motion-blur.c
new file mode 100644
index 0000000..baab51b
--- /dev/null
+++ b/operations/common/motion-blur.c
@@ -0,0 +1,174 @@
+/* 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 2006 �yvind Kolås <pippin gimp org>
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+#include <math.h>
+
+#ifdef GEGL_CHANT_PROPERTIES
+
+
+gegl_chant_double   (length, _("Length"), 0.0, 200.0, 10.0,
+                  _("Length of blur in pixels"))
+gegl_chant_double   (angle,  _("Angle"),  -360, 360, 0,
+                  _("Angle of blur in degrees"))
+
+#else
+
+#define GEGL_CHANT_TYPE_AREA_FILTER
+#define GEGL_CHANT_C_FILE       "motion-blur.c"
+
+#include "gegl-chant.h"
+
+static void
+prepare (GeglOperation *operation)
+{
+  GeglOperationAreaFilter* op_area = GEGL_OPERATION_AREA_FILTER (operation);
+  GeglChantO* o = GEGL_CHANT_PROPERTIES (operation);
+
+  gdouble theta = o->angle * M_PI / 180.0;
+  gdouble offset_x = fabs(o->length * cos(theta));
+  gdouble offset_y = fabs(o->length * sin(theta));
+
+  op_area->left   =
+  op_area->right  = (gint)ceil(0.5 * offset_x);
+  op_area->top    =
+  op_area->bottom = (gint)ceil(0.5 * offset_y);
+
+  gegl_operation_set_format (operation, "output", babl_format ("RaGaBaA float"));
+}
+
+static inline gfloat*
+get_pixel_color(gfloat* in_buf, 
+                const GeglRectangle* rect, 
+                gint x,
+                gint y)
+{
+  gint ix = x - rect->x;
+  gint iy = y - rect->y;
+  ix = CLAMP(ix, 0, rect->width-1);
+  iy = CLAMP(iy, 0, rect->height-1);
+  
+  return &in_buf[(iy*rect->width + ix) * 4];
+}
+
+static gboolean
+process (GeglOperation       *operation,
+         GeglBuffer          *input,
+         GeglBuffer          *output,
+         const GeglRectangle *roi)
+{
+  GeglRectangle src_rect;
+  GeglChantO *o = GEGL_CHANT_PROPERTIES (operation);
+  GeglOperationAreaFilter *op_area;
+  gfloat* in_buf;
+  gfloat* out_buf;
+  gfloat* out_pixel;
+  gint x,y;
+  
+  gdouble theta = o->angle * M_PI / 180.0;
+  gdouble offset_x = o->length * cos(theta);
+  gdouble offset_y = o->length * sin(theta);
+  gint num_steps = (gint)ceil(o->length) + 1;
+  gfloat inv_num_steps = 1.0f / num_steps;
+
+  op_area = GEGL_OPERATION_AREA_FILTER (operation);
+
+  src_rect = *roi;
+  src_rect.x -= op_area->left;
+  src_rect.y -= op_area->top;
+  src_rect.width += op_area->left + op_area->right;
+  src_rect.height += op_area->top + op_area->bottom;
+
+  in_buf = g_new (gfloat, src_rect.width * src_rect.height * 4);
+  out_buf = g_new0 (gfloat, roi->width * roi->height * 4);
+  out_pixel = out_buf;
+
+  gegl_buffer_get (input, 1.0, &src_rect, babl_format ("RaGaBaA float"), in_buf, GEGL_AUTO_ROWSTRIDE);
+    
+  for (y=0; y<roi->height; ++y)
+    {
+      for (x=0; x<roi->width; ++x)
+        {
+          gint step;
+          gint c;
+          gint px = x+roi->x;
+          gint py = y+roi->y;
+          gfloat sum[4] = {0,0,0,0};
+          for (step=0; step<num_steps; ++step)
+            {
+              gdouble t = num_steps == 1 ? 0.0 : step / (gdouble)(num_steps-1) - 0.5;
+              
+              /* get the interpolated pixel position for this step */
+              gdouble xx = px + t*offset_x;
+              gdouble yy = py + t*offset_y;
+              gint ix = (gint)floor(xx);
+              gint iy = (gint)floor(yy);
+              gdouble dx = xx - floor(xx);
+              gdouble dy = yy - floor(yy);
+
+              /* do bilinear interpolation to get a nice smooth result */
+              gfloat *pix0, *pix1, *pix2, *pix3;
+              gfloat mixy0[4];
+              gfloat mixy1[4];
+              
+              pix0 = get_pixel_color(in_buf, &src_rect, ix, iy);
+              pix1 = get_pixel_color(in_buf, &src_rect, ix+1, iy);
+              pix2 = get_pixel_color(in_buf, &src_rect, ix, iy+1);
+              pix3 = get_pixel_color(in_buf, &src_rect, ix+1, iy+1);
+              for (c=0; c<4; ++c)
+                {
+                  mixy0[c] = dy*(pix2[c] - pix0[c]) + pix0[c];
+                  mixy1[c] = dy*(pix3[c] - pix1[c]) + pix1[c];
+                  sum[c] += dx*(mixy1[c] - mixy0[c]) + mixy0[c];
+                }
+            }
+            
+          for (c=0; c<4; ++c)
+            *out_pixel++ = sum[c] * inv_num_steps;
+        }
+    }
+  
+  gegl_buffer_set (output, roi, babl_format ("RaGaBaA float"), out_buf, GEGL_AUTO_ROWSTRIDE);
+  
+  g_free (in_buf);
+  g_free (out_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;
+
+  operation_class->name        = "gegl:motion-blur";
+  operation_class->categories  = "blur";
+  operation_class->description = _("Linear motion blur");
+}
+
+#endif