[gegl] Add gegl:antialias (imported from GIMP)

[Barak Itkin <barakitkin src gnome org>]

commit 30811191567ab1f2557b9af2993a3d0cad6e26c3
Author: Barak Itkin <lightningismyname gmail com>
Date:   Sat Aug 3 19:21:42 2013 +0300

    Add gegl:antialias (imported from GIMP)

 operations/common/antialias.c |  269 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 269 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/antialias.c b/operations/common/antialias.c
new file mode 100644
index 0000000..44cba19
--- /dev/null
+++ b/operations/common/antialias.c
@@ -0,0 +1,269 @@
+/* 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/>.
+ *
+ * This operation is a port of the GIMP antialias plugin:
+ *
+ *     Auntie Alias 0.92 --- image filter plug-in
+ *     Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *     Copyright (C) 2005 Adam D. Moss (adam gimp org)
+ *
+ * The porting to GEGL was done by Barak Itkin
+ *
+ *     Copyright 2013 Barak Itkin <lightningismyname gmail com>
+ */
+
+/* This plugin performs a pseudo-antialiasing effect on hard-edged source
+ * material.  It does this by performing a 'clever' edge extrapolation for
+ * each pixel which is then resampled back to a single pixel for output.
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+#include <math.h>
+
+#ifdef GEGL_CHANT_PROPERTIES
+
+/* This operation has no properties */
+
+#else
+
+#define GEGL_CHANT_TYPE_AREA_FILTER
+#define GEGL_CHANT_C_FILE           "antialias.c"
+
+#include "gegl-chant.h"
+
+static void
+prepare (GeglOperation *operation)
+{
+  const Babl *input_format = gegl_operation_get_source_format (operation, "input");
+  const Babl *format;
+
+  GeglOperationAreaFilter *op_area = GEGL_OPERATION_AREA_FILTER (operation);
+
+  if (input_format == NULL || babl_format_has_alpha (input_format))
+    format = babl_format ("RGBA float");
+  else
+    format = babl_format ("RGB float");
+
+  gegl_operation_set_format (operation, "input", format);
+  gegl_operation_set_format (operation, "output", format);
+
+  op_area->left   =
+  op_area->right  =
+  op_area->top    =
+  op_area->bottom = 1;
+}
+
+static int
+extrapolate9 (const int components,
+              gfloat *E0, gfloat *E1, gfloat *E2,
+              gfloat *E3, gfloat *E4, gfloat *E5,
+              gfloat *E6, gfloat *E7, gfloat *E8,
+              gfloat *A,  gfloat *B,  gfloat *C,
+              gfloat *D,  gfloat *E,  gfloat *F,
+              gfloat *G,  gfloat *H,  gfloat *I)
+{
+#define PEQ(X,Y)      (0 == memcmp ((X), (Y), components * sizeof(gfloat)))
+#define PCPY(DST,SRC) memcpy ((DST), (SRC), components * sizeof(gfloat))
+
+  /* an implementation of the Scale3X edge-extrapolation algorithm */
+  if ( (!PEQ(B,H)) && (!PEQ(D,F)) )
+    {
+      if (PEQ(D,B)) PCPY(E0,D); else PCPY(E0,E);
+      if ((PEQ(D,B) && !PEQ(E,C)) || (PEQ(B,F) && !PEQ(E,A)))
+        PCPY(E1,B); else PCPY(E1,E);
+      if (PEQ(B,F)) PCPY(E2,F); else PCPY(E2,E);
+      if ((PEQ(D,B) && !PEQ(E,G)) || (PEQ(D,H) && !PEQ(E,A)))
+        PCPY(E3,D); else PCPY(E3,E);
+      PCPY(E4,E);
+      if ((PEQ(B,F) && !PEQ(E,I)) || (PEQ(H,F) && !PEQ(E,C)))
+        PCPY(E5,F); else PCPY(E5,E);
+      if (PEQ(D,H)) PCPY(E6,D); else PCPY(E6,E);
+      if ((PEQ(D,H) && !PEQ(E,I)) || (PEQ(H,F) && !PEQ(E,G)))
+        PCPY(E7,H); else PCPY(E7,E);
+      if (PEQ(H,F)) PCPY(E8,F); else PCPY(E8,E);
+      return 1;
+    }
+  else
+    {
+      return 0;
+    }
+
+#undef PEQ
+#undef PCPY
+}
+
+static gboolean
+process (GeglOperation       *operation,
+         GeglBuffer          *input,
+         GeglBuffer          *output,
+         const GeglRectangle *roi,
+         gint                 level)
+{
+  gint          components;
+  gint          col, c;
+  gfloat       *rowbefore;
+  gfloat       *rowthis;
+  gfloat       *rowafter;
+  gfloat       *dest;
+  gfloat       *ninepix;
+  gboolean      has_alpha;
+  guint         alpha;
+  const Babl   *format = gegl_operation_get_format (operation, "input");
+
+  /* The rectangle of the current row we are working on */
+  GeglRectangle rowrect;
+
+  /* The rectangle of the sample we are going to take for the
+   * next line (this does include the interpolation distance!) */
+  GeglRectangle rownext_bufrect;
+
+  components = babl_format_get_n_components (format);
+  has_alpha  = babl_format_has_alpha (format);
+  alpha      = components - 1;
+
+  /* The original algorithm that appeared in GIMP did a manual clamping
+   * of samples outside the input rectangle, by always allocating a
+   * buffer which is 1-pixel wider than necessary, and then filling the
+   * edges of the buffer with repetitions of the edges.
+   * We don't need this complexity here thanks to the CLAMP abyss policy
+   * which is implemented by GEGL. We still allocate buffers which are
+   * larger, but we let GEGL fill the edges with the clamped values.
+   */
+
+  rowbefore  = g_new (gfloat, (roi->width + 2) * components);
+  rowthis    = g_new (gfloat, (roi->width + 2) * components);
+  rowafter   = g_new (gfloat, (roi->width + 2) * components);
+  dest       = g_new (gfloat, roi->width * components);
+  ninepix    = g_new (gfloat, 9 * components);
+
+  gegl_rectangle_set (&rowrect, roi->x, roi->y, roi->width, 1);
+  gegl_rectangle_set (&rownext_bufrect, roi->x - 1, roi->y - 1, roi->width + 2, 1);
+
+  gegl_buffer_get (input, &rownext_bufrect, 1.0, format,
+                   rowbefore, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_CLAMP);
+  ++rownext_bufrect.y;
+
+  gegl_buffer_get (input, &rownext_bufrect, 1.0, format,
+                   rowthis, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_CLAMP);
+  ++rownext_bufrect.y;
+
+  gegl_buffer_get (input, &rownext_bufrect, 1.0, format,
+                   rowafter, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_CLAMP);
+  ++rownext_bufrect.y;
+
+  for (rowrect.y = roi->y; rowrect.y < (roi->y + roi->height); ++rowrect.y)
+    {
+      gfloat *tmp;
+
+      /* this macro returns the current pixel if it has some opacity. Otherwise
+       * it returns the center pixel of the current 3x3 area. */
+#define USE_IF_ALPHA(p) (((!has_alpha) || *((p)+alpha)) ? (p) : &rowthis[(col+1) * components])
+
+      for (col = 0; col < roi->width; ++col)
+        {
+          /* do 9x extrapolation pass */
+          if (((!has_alpha) || (rowthis[(col + 1) * components + alpha] > 0)) &&
+              extrapolate9 (components,
+                            &ninepix[0 * components],
+                            &ninepix[1 * components],
+                            &ninepix[2 * components],
+                            &ninepix[3 * components],
+                            &ninepix[4 * components],
+                            &ninepix[5 * components],
+                            &ninepix[6 * components],
+                            &ninepix[7 * components],
+                            &ninepix[8 * components],
+                            USE_IF_ALPHA (&rowbefore[(col + 0) * components]),
+                            USE_IF_ALPHA (&rowbefore[(col + 1) * components]),
+                            USE_IF_ALPHA (&rowbefore[(col + 2) * components]),
+                            USE_IF_ALPHA (&rowthis  [(col + 0) * components]),
+                                          &rowthis  [(col + 1) * components],
+                            USE_IF_ALPHA (&rowthis  [(col + 2) * components]),
+                            USE_IF_ALPHA (&rowafter [(col + 0) * components]),
+                            USE_IF_ALPHA (&rowafter [(col + 1) * components]),
+                            USE_IF_ALPHA (&rowafter [(col + 2) * components])
+                            ))
+            {
+              /* subsample results and put into dest */
+              for (c = 0; c < components; ++c)
+                {
+#define NINEPIX(index, c) ninepix[(index) * components + (c)]
+                  dest[(col * components) + c] =
+                    (3 * NINEPIX(0, c) + 5 * NINEPIX(1, c) + 3 * NINEPIX(2, c) +
+                     5 * NINEPIX(3, c) + 6 * NINEPIX(4, c) + 5 * NINEPIX(5, c) +
+                     3 * NINEPIX(6, c) + 5 * NINEPIX(7, c) + 3 * NINEPIX(8, c)
+                    /* The GIMP implementation added 19 (out of 255) here before
+                     * normalizing (dividing by 38), which is equivalent to a
+                     * call to "ceil". We don't need this since we are working
+                     * with floating point numbers... */
+                    ) / 38;
+#undef NINEPIX
+                }
+            }
+          else
+            {
+              memcpy (&dest[col * components], &rowthis[(col + 1) * components], components * 
sizeof(gfloat));
+            }
+        }
+
+#undef USE_IF_ALPHA
+
+      /* write result row to dest */
+      gegl_buffer_set (output, &rowrect, 1, format, &dest[0], GEGL_AUTO_ROWSTRIDE);
+
+      /* rotate pointers */
+      tmp       = rowbefore;
+      rowbefore = rowthis;
+      rowthis   = rowafter;
+      rowafter  = tmp;
+
+      /* populate new after-row */
+      gegl_buffer_get (input, &rownext_bufrect, 1.0, format,
+                       rowafter, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_CLAMP);
+      ++rownext_bufrect.y;
+    }
+
+  g_free (rowbefore);
+  g_free (rowthis);
+  g_free (rowafter);
+  g_free (dest);
+  g_free (ninepix);
+
+  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);
+
+  operation_class->prepare = prepare;
+  filter_class->process    = process;
+
+  gegl_operation_class_set_keys (operation_class,
+    "name",        "gegl:antialias",
+    "categories",  "enhance",
+    "description", _("Antialias using the Scale3X edge-extrapolation algorithm"),
+    NULL);
+}
+
+#endif
+