[gegl] operations: add stretch-contrast-hsv ported from gimp plug-ins

[Téo Mazars <teom src gnome org>]

commit 5cac88cd9b77d1cf349ce323f5c5ecbe53d97036
Author: Carlos Zubieta <czubieta dev gmail com>
Date:   Sun Apr 21 15:30:18 2013 -0500

    operations: add stretch-contrast-hsv ported from gimp plug-ins

 operations/common/stretch-contrast-hsv.c |  194 ++++++++++++++++++++++++++++++
 1 files changed, 194 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/stretch-contrast-hsv.c b/operations/common/stretch-contrast-hsv.c
new file mode 100644
index 0000000..33b54dd
--- /dev/null
+++ b/operations/common/stretch-contrast-hsv.c
@@ -0,0 +1,194 @@
+/* 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 1996 Federico Mena Quintero
+ * Copyright 1997 Scott Goehring
+ * Copyright 2006 Øyvind Kolås <pippin gimp org>
+ * Copyright 2013 Carlos Zubieta <czubieta dev gmail com>
+ *
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+
+#ifdef GEGL_CHANT_PROPERTIES
+
+#else
+
+#define GEGL_CHANT_TYPE_FILTER
+#define GEGL_CHANT_C_FILE "stretch-contrast-hsv.c"
+
+#include "gegl-chant.h"
+
+typedef struct {
+  gfloat slo;
+  gfloat sdiff;
+  gfloat vlo;
+  gfloat vdiff;
+} AutostretchData;
+
+static void
+buffer_get_auto_strech_data (GeglBuffer      *buffer,
+                             AutostretchData *data)
+{
+  gfloat smin =  G_MAXFLOAT;
+  gfloat smax = -G_MAXFLOAT;
+  gfloat vmin =  G_MAXFLOAT;
+  gfloat vmax = -G_MAXFLOAT;
+
+  GeglBufferIterator *gi;
+
+  gi = gegl_buffer_iterator_new (buffer, NULL, 0, babl_format ("HSVA float"),
+                                 GEGL_BUFFER_READ, GEGL_ABYSS_NONE);
+
+  while (gegl_buffer_iterator_next (gi))
+    {
+      gfloat *buf = gi->data[0];
+      gint    i;
+
+      for (i = 0; i < gi->length; i++)
+        {
+          gfloat sval = buf[1];
+          gfloat vval = buf[2];
+
+          smin = MIN (sval, smin);
+          smax = MAX (sval, smax);
+          vmin = MIN (vval, vmin);
+          vmax = MAX (vval, vmax);
+
+          buf += 4;
+        }
+    }
+
+  if (data)
+    {
+      data->slo   = smin;
+      data->sdiff = smax - smin;
+      data->vlo   = vmin;
+      data->vdiff = vmax - vmin;
+    }
+}
+
+static void
+clean_autostretch_data (AutostretchData *data)
+{
+  if (data->sdiff < 1e-5)
+    {
+      data->sdiff = 1.0;
+      data->slo   = 0.0;
+    }
+
+  if (data->vdiff < 1e-5)
+    {
+      data->vdiff = 1.0;
+      data->vlo   = 0.0;
+    }
+}
+
+static void
+prepare (GeglOperation *operation)
+{
+  gegl_operation_set_format (operation, "input",  babl_format ("HSVA float"));
+  gegl_operation_set_format (operation, "output", babl_format ("HSVA float"));
+}
+
+static GeglRectangle
+get_required_for_output (GeglOperation       *operation,
+                         const gchar         *input_pad,
+                         const GeglRectangle *roi)
+{
+  GeglRectangle *result;
+  result = gegl_operation_source_get_bounding_box (operation, "input");
+
+  if (result != NULL)
+    return *result;
+  else
+    return *GEGL_RECTANGLE (0, 0, 0, 0);
+}
+
+static GeglRectangle
+get_cached_region (GeglOperation       *operation,
+                   const GeglRectangle *roi)
+{
+  return get_required_for_output (operation, "input", roi);
+}
+
+static gboolean
+process (GeglOperation       *operation,
+         GeglBuffer          *input,
+         GeglBuffer          *output,
+         const GeglRectangle *result,
+         gint                 level)
+{
+  AutostretchData     data;
+  GeglBufferIterator *gi;
+
+  buffer_get_auto_strech_data (input, &data);
+  clean_autostretch_data (&data);
+
+  gi = gegl_buffer_iterator_new (input, result, 0, babl_format ("HSVA float"),
+                                 GEGL_BUFFER_READ, GEGL_ABYSS_NONE);
+
+  gegl_buffer_iterator_add (gi, output, result, 0, babl_format ("HSVA float"),
+                            GEGL_BUFFER_WRITE, GEGL_ABYSS_NONE);
+
+  while (gegl_buffer_iterator_next (gi))
+    {
+      gfloat *in  = gi->data[0];
+      gfloat *out = gi->data[1];
+      gint    i;
+
+      for (i = 0; i < gi->length; i++)
+        {
+          out[0] = in[0]; /* Keep hue */
+          out[1] = (in[1] - data.slo) / data.sdiff;
+          out[2] = (in[2] - data.vlo) / data.vdiff;
+          out[3] = in[3]; /* Keep alpha */
+
+          in  += 4;
+          out += 4;
+        }
+    }
+
+  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->get_required_for_output = get_required_for_output;
+  operation_class->get_cached_region       = get_cached_region;
+
+  gegl_operation_class_set_keys (operation_class,
+    "name"       , "gegl:stretch-contrast-hsv",
+    "categories" , "color:enhance",
+    "description",
+        _("Scales the components of the buffer to be in the 0.0-1.0 range. "
+          "This improves images that make poor use of the available contrast "
+          "(little contrast, very dark, or very bright images). "
+          "This version differs from Contrast Autostretch in that it works "
+          "in HSV scpace, and preserves hue."),
+        NULL);
+}
+
+#endif