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+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationdesaturate.c
+ * Copyright (C) 2007 Michael Natterer <mitch@gimp.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <cairo.h>
+#include <gegl.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "libgimpcolor/gimpcolor.h"
+#include "libgimpconfig/gimpconfig.h"
+
+#include "operations-types.h"
+
+#include "gimpoperationdesaturate.h"
+
+#include "gimp-intl.h"
+
+
+enum
+{
+ PROP_0,
+ PROP_MODE
+};
+
+
+static void gimp_operation_desaturate_get_property (GObject *object,
+ guint property_id,
+ GValue *value,
+ GParamSpec *pspec);
+static void gimp_operation_desaturate_set_property (GObject *object,
+ guint property_id,
+ const GValue *value,
+ GParamSpec *pspec);
+
+static void gimp_operation_desaturate_prepare (GeglOperation *operation);
+static gboolean gimp_operation_desaturate_process (GeglOperation *operation,
+ void *in_buf,
+ void *out_buf,
+ glong samples,
+ const GeglRectangle *roi,
+ gint level);
+
+
+G_DEFINE_TYPE (GimpOperationDesaturate, gimp_operation_desaturate,
+ GIMP_TYPE_OPERATION_POINT_FILTER)
+
+#define parent_class gimp_operation_desaturate_parent_class
+
+
+static void
+gimp_operation_desaturate_class_init (GimpOperationDesaturateClass *klass)
+{
+ GObjectClass *object_class = G_OBJECT_CLASS (klass);
+ GeglOperationClass *operation_class = GEGL_OPERATION_CLASS (klass);
+ GeglOperationPointFilterClass *point_class = GEGL_OPERATION_POINT_FILTER_CLASS (klass);
+
+ object_class->set_property = gimp_operation_desaturate_set_property;
+ object_class->get_property = gimp_operation_desaturate_get_property;
+
+ operation_class->prepare = gimp_operation_desaturate_prepare;
+
+ point_class->process = gimp_operation_desaturate_process;
+
+ gegl_operation_class_set_keys (operation_class,
+ "name", "gimp:desaturate",
+ "categories", "color",
+ "description", _("Turn colors into shades of gray"),
+ NULL);
+
+ GIMP_CONFIG_PROP_ENUM (object_class, PROP_MODE,
+ "mode",
+ _("Mode"),
+ _("Choose shade of gray based on"),
+ GIMP_TYPE_DESATURATE_MODE,
+ GIMP_DESATURATE_LUMINANCE,
+ GIMP_PARAM_STATIC_STRINGS);
+}
+
+static void
+gimp_operation_desaturate_init (GimpOperationDesaturate *self)
+{
+}
+
+static void
+gimp_operation_desaturate_get_property (GObject *object,
+ guint property_id,
+ GValue *value,
+ GParamSpec *pspec)
+{
+ GimpOperationDesaturate *desaturate = GIMP_OPERATION_DESATURATE (object);
+
+ switch (property_id)
+ {
+ case PROP_MODE:
+ g_value_set_enum (value, desaturate->mode);
+ break;
+
+ default:
+ G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+ break;
+ }
+}
+
+static void
+gimp_operation_desaturate_set_property (GObject *object,
+ guint property_id,
+ const GValue *value,
+ GParamSpec *pspec)
+{
+ GimpOperationDesaturate *desaturate = GIMP_OPERATION_DESATURATE (object);
+
+ switch (property_id)
+ {
+ case PROP_MODE:
+ desaturate->mode = g_value_get_enum (value);
+ break;
+
+ default:
+ G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+ break;
+ }
+}
+
+static void
+gimp_operation_desaturate_prepare (GeglOperation *operation)
+{
+ GimpOperationDesaturate *desaturate = GIMP_OPERATION_DESATURATE (operation);
+ const Babl *format = gegl_operation_get_source_format (operation, "input");
+
+ if (desaturate->mode == GIMP_DESATURATE_LUMINANCE)
+ {
+ format = babl_format_with_space ("RGBA float", format);
+ }
+ else
+ {
+ format = babl_format_with_space ("R'G'B'A float", format);
+ }
+
+ gegl_operation_set_format (operation, "input", format);
+ gegl_operation_set_format (operation, "output", format);
+}
+
+static gboolean
+gimp_operation_desaturate_process (GeglOperation *operation,
+ void *in_buf,
+ void *out_buf,
+ glong samples,
+ const GeglRectangle *roi,
+ gint level)
+{
+ GimpOperationDesaturate *desaturate = GIMP_OPERATION_DESATURATE (operation);
+ gfloat *src = in_buf;
+ gfloat *dest = out_buf;
+
+ switch (desaturate->mode)
+ {
+ case GIMP_DESATURATE_LIGHTNESS:
+ /* This is the formula for Lightness in the HSL "bi-hexcone"
+ * model: https://en.wikipedia.org/wiki/HSL_and_HSV
+ */
+ while (samples--)
+ {
+ gfloat min, max, value;
+
+ max = MAX (src[0], src[1]);
+ max = MAX (max, src[2]);
+ min = MIN (src[0], src[1]);
+ min = MIN (min, src[2]);
+
+ value = (max + min) / 2;
+
+ dest[0] = value;
+ dest[1] = value;
+ dest[2] = value;
+ dest[3] = src[3];
+
+ src += 4;
+ dest += 4;
+ }
+ break;
+
+ case GIMP_DESATURATE_LUMA:
+ case GIMP_DESATURATE_LUMINANCE:
+ while (samples--)
+ {
+ gfloat value = GIMP_RGB_LUMINANCE (src[0], src[1], src[2]);
+
+ dest[0] = value;
+ dest[1] = value;
+ dest[2] = value;
+ dest[3] = src[3];
+
+ src += 4;
+ dest += 4;
+ }
+ break;
+
+ case GIMP_DESATURATE_AVERAGE:
+ /* This is the formula for Intensity in the HSI model:
+ * https://en.wikipedia.org/wiki/HSL_and_HSV
+ */
+ while (samples--)
+ {
+ gfloat value = (src[0] + src[1] + src[2]) / 3;
+
+ dest[0] = value;
+ dest[1] = value;
+ dest[2] = value;
+ dest[3] = src[3];
+
+ src += 4;
+ dest += 4;
+ }
+ break;
+
+ case GIMP_DESATURATE_VALUE:
+ /* This is the formula for Value in the HSV model:
+ * https://en.wikipedia.org/wiki/HSL_and_HSV
+ */
+ while (samples--)
+ {
+ gfloat value;
+
+ value = MAX (src[0], src[1]);
+ value = MAX (value, src[2]);
+
+ dest[0] = value;
+ dest[1] = value;
+ dest[2] = value;
+ dest[3] = src[3];
+
+ src += 4;
+ dest += 4;
+ }
+ break;
+ }
+
+ return TRUE;
+}