[gegl] operations: port GIMP's max-rgb filter to a gegl operation

[Barak Itkin <barakitkin src gnome org>]

commit a02660ab1c4285a17cb3e934b200635bb18cfa70
Author: Barak Itkin <lightningismyname gmail com>
Date:   Wed Feb 2 01:04:11 2011 +0200

    operations: port GIMP's max-rgb filter to a gegl operation

 operations/workshop/max-rgb.c |  121 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 121 insertions(+), 0 deletions(-)
---
diff --git a/operations/workshop/max-rgb.c b/operations/workshop/max-rgb.c
new file mode 100644
index 0000000..a8a952e
--- /dev/null
+++ b/operations/workshop/max-rgb.c
@@ -0,0 +1,121 @@
+/* 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 (C) 2011 Barak Itkin <lightningismyname gmail org>
+ *
+ * Based on "Maximum RGB" GIMP plugin
+ * Copyright (C) 1997 Shuji Narazaki <narazaki InetQ or jp>
+ * Copyright (C) 2000 tim copperfield <timecop japan co jp>
+ *
+ * The common/brightness-contrast.c operation by Øyvind Kolås was used
+ * as a template for this op file.
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+
+#ifdef GEGL_CHANT_PROPERTIES
+gegl_chant_boolean (min,   _("Minimal"),   FALSE,
+                    _("Hold the minimal values instead of the maximal values"))
+
+#else
+
+#define GEGL_CHANT_TYPE_POINT_FILTER
+#define GEGL_CHANT_C_FILE       "max-rgb.c"
+
+#include "gegl-chant.h"
+
+
+static void prepare (GeglOperation *operation)
+{
+  gegl_operation_set_format (operation, "input", babl_format ("RGBA float"));
+  gegl_operation_set_format (operation, "output", babl_format ("RGBA float"));
+}
+
+static gboolean
+process (GeglOperation       *op,
+         void                *in_buf,
+         void                *out_buf,
+         glong                n_pixels,
+         const GeglRectangle *roi)
+{
+  GeglChantO *o = GEGL_CHANT_PROPERTIES (op);
+  gfloat     * GEGL_ALIGNED in_pixel;
+  gfloat     * GEGL_ALIGNED out_pixel;
+  gfloat      val;
+  glong       i;
+
+  in_pixel   = in_buf;
+  out_pixel  = out_buf;
+
+  /* The code could be compacted by inserting the if into the loop, but
+   * it's more efficient if we do it like this. Note also that in cases
+   * of equality between the maximal/minimal channels, we want to keep
+   * them all.
+   */
+  if (!o->min)
+    {
+      for (i=0; i<n_pixels; i++)
+        {
+          val = MAX (in_pixel[0], MAX (in_pixel[1], in_pixel[2]));
+
+          out_pixel[0] = (in_pixel[0] == val) ? val : 0;
+          out_pixel[1] = (in_pixel[1] == val) ? val : 0;
+          out_pixel[2] = (in_pixel[2] == val) ? val : 0;
+
+          out_pixel[3] = in_pixel[3]; /* copy the alpha */
+
+          in_pixel  += 4;
+          out_pixel += 4;
+        }
+    }
+  else
+    {
+      for (i=0; i<n_pixels; i++)
+        {
+          val = MIN (in_pixel[0], MIN (in_pixel[1], in_pixel[2]));
+
+          out_pixel[0] = (in_pixel[0] == val) ? val : 0;
+          out_pixel[1] = (in_pixel[1] == val) ? val : 0;
+          out_pixel[2] = (in_pixel[2] == val) ? val : 0;
+
+          out_pixel[3] = in_pixel[3]; /* copy the alpha */
+
+          in_pixel  += 4;
+          out_pixel += 4;
+        }
+    }
+
+  return TRUE;
+}
+
+static void
+gegl_chant_class_init (GeglChantClass *klass)
+{
+  GeglOperationClass            *operation_class;
+  GeglOperationPointFilterClass *point_filter_class;
+
+  operation_class    = GEGL_OPERATION_CLASS (klass);
+  point_filter_class = GEGL_OPERATION_POINT_FILTER_CLASS (klass);
+
+  operation_class->prepare = prepare;
+  point_filter_class->process = process;
+
+  operation_class->name        = "gegl:max-rgb";
+  operation_class->categories  = "color";
+  operation_class->description = _("Reduce image to pure red, green, and blue");
+}
+
+#endif