[gegl] color-overlay: add new operation to workshop

[N/A <ell src gnome org>]

commit 224637b936cdecce856db9d052d515c5bffd1ff7
Author: Ell <ell_se yahoo com>
Date:   Fri Mar 2 12:05:46 2018 -0500

    color-overlay: add new operation to workshop
    
    A simple op, blending a constant color with the input, preserving
    its transparency.  Equivalent to gegl:dst-atop with a gegl:color
    aux.
    
    We could have just added a "value" property to dst-atop, but since
    it wouldn't be very useful for the other Porter-Duff ops, just add
    a dedicated op.

 operations/workshop/Makefile.am     |    1 +
 operations/workshop/color-overlay.c |  163 +++++++++++++++++++++++++++++++++++
 po/POTFILES.in                      |    1 +
 3 files changed, 165 insertions(+), 0 deletions(-)
---
diff --git a/operations/workshop/Makefile.am b/operations/workshop/Makefile.am
index 10784f1..f6b4f8d 100644
--- a/operations/workshop/Makefile.am
+++ b/operations/workshop/Makefile.am
@@ -12,6 +12,7 @@ opdir = $(ext_dir)
 op_LTLIBRARIES = \
        bayer-matrix.la \
        bilateral-filter-fast.la \
+       color-overlay.la \
        demosaic-bimedian.la \
        demosaic-simple.la \
        ditto.la \
diff --git a/operations/workshop/color-overlay.c b/operations/workshop/color-overlay.c
new file mode 100644
index 0000000..9cf8637
--- /dev/null
+++ b/operations/workshop/color-overlay.c
@@ -0,0 +1,163 @@
+/* This file is an image processing operation for GEGL
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (C) 2018 Ell
+ */
+
+#include "config.h"
+#include <glib/gi18n-lib.h>
+
+#define EPSILON 1e-6
+
+#ifdef GEGL_PROPERTIES
+
+property_color (value, _("Color"), "transparent")
+    description (_("The color to paint over the input"))
+    ui_meta     ("role", "color-primary")
+
+property_boolean (srgb, _("sRGB"), FALSE)
+    description (_("Use sRGB gamma instead of linear"))
+
+#else
+
+#define GEGL_OP_POINT_FILTER
+#define GEGL_OP_NAME     color_overlay
+#define GEGL_OP_C_SOURCE color-overlay.c
+
+#include "gegl-op.h"
+
+static void prepare (GeglOperation *operation)
+{
+  GeglProperties *o = GEGL_PROPERTIES (operation);
+  const Babl     *format;
+
+  if (! o->srgb)
+    format = babl_format ("RGBA float");
+  else
+    format = babl_format ("R'G'B'A float");
+
+  gegl_operation_set_format (operation, "input", format);
+  gegl_operation_set_format (operation, "output", format);
+}
+
+static gboolean
+process (GeglOperation       *operation,
+         void                *in_buf,
+         void                *out_buf,
+         glong                samples,
+         const GeglRectangle *roi,
+         gint                 level)
+{
+  GeglProperties *o   = GEGL_PROPERTIES (operation);
+  gfloat         *in  = in_buf;
+  gfloat         *out = out_buf;
+  const Babl     *format;
+  gfloat          color[4];
+  gfloat          alpha_c;
+
+  if (! o->srgb)
+    format = babl_format ("RaGaBaA float");
+  else
+    format = babl_format ("R'aG'aB'aA float");
+
+  gegl_color_get_pixel (o->value, format, &color);
+
+  alpha_c = 1.0f - color[3];
+
+  if (fabs (alpha_c) <= EPSILON)
+    {
+      while (samples--)
+        {
+          gint i;
+
+          for (i = 0; i < 3; i++)
+            out[i] = color[i];
+
+          out[3] = in[3];
+
+          in  += 4;
+          out += 4;
+        }
+    }
+  else
+    {
+      while (samples--)
+        {
+          gint i;
+
+          for (i = 0; i < 3; i++)
+            out[i] = in[i] * alpha_c + color[i];
+
+          out[3] = in[3];
+
+          in  += 4;
+          out += 4;
+        }
+    }
+
+  return TRUE;
+}
+
+static gboolean
+operation_process (GeglOperation        *operation,
+                   GeglOperationContext *context,
+                   const gchar          *output_prop,
+                   const GeglRectangle  *result,
+                   gint                  level)
+{
+  GeglProperties *o = GEGL_PROPERTIES (operation);
+  gdouble         alpha;
+
+  gegl_color_get_rgba (o->value, NULL, NULL, NULL, &alpha);
+
+  if (fabs (alpha) <= EPSILON)
+    {
+      /* pass input directly */
+      gegl_operation_context_set_object (
+        context,
+        "output", gegl_operation_context_get_object (context, "input"));
+
+      return TRUE;
+    }
+
+  return GEGL_OPERATION_CLASS (gegl_op_parent_class)->process (
+    operation, context, output_prop, result, level);
+}
+
+static void
+gegl_op_class_init (GeglOpClass *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;
+  operation_class->process    = operation_process;
+
+  point_filter_class->process = process;
+
+  gegl_operation_class_set_keys (operation_class,
+      "name",       "gegl:color-overlay",
+      "categories", "color",
+      "title",      _("Color Overlay"),
+      "description", _("Paint a color overlay over the input, "
+                       "preseving its transparency."),
+      NULL);
+}
+
+#endif
+
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 3b2bf53..7bc3d36 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -236,6 +236,7 @@ operations/transform/transform-core.c
 operations/transform/translate.c
 operations/workshop/bayer-matrix.c
 operations/workshop/bilateral-filter-fast.c
+operations/workshop/color-overlay.c
 operations/workshop/demosaic-bimedian.c
 operations/workshop/demosaic-simple.c
 operations/workshop/ditto.c