1 files changed, 126 insertions, 0 deletions
diff --git a/app/operations/layer-modes-legacy/gimpoperationdifferencelegacy.c b/app/operations/layer-modes-legacy/gimpoperationdifferencelegacy.c
new file mode 100644
index 0000000..55f3328
--- /dev/null
+++ b/app/operations/layer-modes-legacy/gimpoperationdifferencelegacy.c
@@ -0,0 +1,126 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationdifferencemode.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ *               2012 Ville Sokk <ville.sokk@gmail.com>
+ *
+ * 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 <gegl-plugin.h>
+
+#include "../operations-types.h"
+
+#include "gimpoperationdifferencelegacy.h"
+
+
+static gboolean   gimp_operation_difference_legacy_process (GeglOperation       *op,
+                                                            void                *in,
+                                                            void                *layer,
+                                                            void                *mask,
+                                                            void                *out,
+                                                            glong                samples,
+                                                            const GeglRectangle *roi,
+                                                            gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationDifferenceLegacy, gimp_operation_difference_legacy,
+               GIMP_TYPE_OPERATION_LAYER_MODE)
+
+
+static void
+gimp_operation_difference_legacy_class_init (GimpOperationDifferenceLegacyClass *klass)
+{
+  GeglOperationClass          *operation_class  = GEGL_OPERATION_CLASS (klass);
+  GimpOperationLayerModeClass *layer_mode_class = GIMP_OPERATION_LAYER_MODE_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name",        "gimp:difference-legacy",
+                                 "description", "GIMP difference mode operation",
+                                 NULL);
+
+  layer_mode_class->process = gimp_operation_difference_legacy_process;
+}
+
+static void
+gimp_operation_difference_legacy_init (GimpOperationDifferenceLegacy *self)
+{
+}
+
+
+static gboolean
+gimp_operation_difference_legacy_process (GeglOperation       *op,
+                                          void                *in_p,
+                                          void                *layer_p,
+                                          void                *mask_p,
+                                          void                *out_p,
+                                          glong                samples,
+                                          const GeglRectangle *roi,
+                                          gint                 level)
+{
+  GimpOperationLayerMode *layer_mode = (gpointer) op;
+  gfloat                 *in         = in_p;
+  gfloat                 *out        = out_p;
+  gfloat                 *layer      = layer_p;
+  gfloat                 *mask       = mask_p;
+  gfloat                  opacity    = layer_mode->opacity;
+
+  while (samples--)
+    {
+      gfloat comp_alpha, new_alpha;
+
+      comp_alpha = MIN (in[ALPHA], layer[ALPHA]) * opacity;
+      if (mask)
+        comp_alpha *= *mask;
+
+      new_alpha = in[ALPHA] + (1.0f - in[ALPHA]) * comp_alpha;
+
+      if (comp_alpha && new_alpha)
+        {
+          gfloat ratio = comp_alpha / new_alpha;
+          gint   b;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              gfloat comp = in[b] - layer[b];
+              comp = (comp < 0.0f) ? -comp : comp;
+
+              out[b] = comp * ratio + in[b] * (1.0f - ratio);
+            }
+        }
+      else
+        {
+          gint b;
+
+          for (b = RED; b < ALPHA; b++)
+            {
+              out[b] = in[b];
+            }
+        }
+
+      out[ALPHA] = in[ALPHA];
+
+      in    += 4;
+      layer += 4;
+      out   += 4;
+
+      if (mask)
+        mask++;
+    }
+
+  return TRUE;
+}