Adding upstream version 2.10.36.upstream/2.10.36

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1215 insertions, 0 deletions

diff --git a/app/operations/layer-modes/gimpoperationlayermode-blend.c b/app/operations/layer-modes/gimpoperationlayermode-blend.c
new file mode 100644
index 0000000..e107462
--- /dev/null
+++ b/app/operations/layer-modes/gimpoperationlayermode-blend.c
@@ -0,0 +1,1215 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode-blend.c
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *               2017 Øyvind Kolås <pippin@gimp.org>
+ *               2017 Ell
+ *
+ * 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 <cairo.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "libgimpcolor/gimpcolor.h"
+#include "libgimpbase/gimpbase.h"
+#include "libgimpmath/gimpmath.h"
+
+#include "../operations-types.h"
+
+#include "gimpoperationlayermode-blend.h"
+
+
+#define EPSILON      1e-6f
+
+#define SAFE_DIV_MIN EPSILON
+#define SAFE_DIV_MAX (1.0f / SAFE_DIV_MIN)
+
+
+/*  local function prototypes  */
+
+static inline gfloat   safe_div (gfloat a,
+                                 gfloat b);
+
+
+/*  private functions  */
+
+
+/* returns a / b, clamped to [-SAFE_DIV_MAX, SAFE_DIV_MAX].
+ * if -SAFE_DIV_MIN <= a <= SAFE_DIV_MIN, returns 0.
+ */
+static inline gfloat
+safe_div (gfloat a,
+          gfloat b)
+{
+  gfloat result = 0.0f;
+
+  if (fabsf (a) > SAFE_DIV_MIN)
+    {
+      result = a / b;
+      result = CLAMP (result, -SAFE_DIV_MAX, SAFE_DIV_MAX);
+    }
+
+  return result;
+}
+
+
+/*  public functions  */
+
+
+/*  non-subtractive blending functions.  these functions must set comp[ALPHA]
+ *  to the same value as layer[ALPHA].  when in[ALPHA] or layer[ALPHA] are
+ *  zero, the value of comp[RED..BLUE] is unconstrained (in particular, it may
+ *  be NaN).
+ */
+
+
+void /* aka linear_dodge */
+gimp_operation_layer_mode_blend_addition (GeglOperation *operation,
+                                          const gfloat  *in,
+                                          const gfloat  *layer,
+                                          gfloat        *comp,
+                                          gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] + layer[c];
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_burn (GeglOperation *operation,
+                                      const gfloat  *in,
+                                      const gfloat  *layer,
+                                      gfloat        *comp,
+                                      gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = 1.0f - safe_div (1.0f - in[c], layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_darken_only (GeglOperation *operation,
+                                             const gfloat  *in,
+                                             const gfloat  *layer,
+                                             gfloat        *comp,
+                                             gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = MIN (in[c], layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_difference (GeglOperation *operation,
+                                            const gfloat  *in,
+                                            const gfloat  *layer,
+                                            gfloat        *comp,
+                                            gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = fabsf (in[c] - layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_divide (GeglOperation *operation,
+                                        const gfloat  *in,
+                                        const gfloat  *layer,
+                                        gfloat        *comp,
+                                        gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = safe_div (in[c], layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_dodge (GeglOperation *operation,
+                                       const gfloat  *in,
+                                       const gfloat  *layer,
+                                       gfloat        *comp,
+                                       gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = safe_div (in[c], 1.0f - layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_exclusion (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = 0.5f - 2.0f * (in[c] - 0.5f) * (layer[c] - 0.5f);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_grain_extract (GeglOperation *operation,
+                                               const gfloat  *in,
+                                               const gfloat  *layer,
+                                               gfloat        *comp,
+                                               gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] - layer[c] + 0.5f;
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_grain_merge (GeglOperation *operation,
+                                             const gfloat  *in,
+                                             const gfloat  *layer,
+                                             gfloat        *comp,
+                                             gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] + layer[c] - 0.5f;
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hard_mix (GeglOperation *operation,
+                                          const gfloat  *in,
+                                          const gfloat  *layer,
+                                          gfloat        *comp,
+                                          gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] + layer[c] < 1.0f ? 0.0f : 1.0f;
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hardlight (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat val;
+
+              if (layer[c] > 0.5f)
+                {
+                  val = (1.0f - in[c]) * (1.0f - (layer[c] - 0.5f) * 2.0f);
+                  val = MIN (1.0f - val, 1.0f);
+                }
+              else
+                {
+                  val = in[c] * (layer[c] * 2.0f);
+                  val = MIN (val, 1.0f);
+                }
+
+              comp[c] = val;
+            }
+        }
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hsl_color (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat dest_min, dest_max, dest_l;
+          gfloat src_min,  src_max,  src_l;
+
+          dest_min = MIN (in[0],  in[1]);
+          dest_min = MIN (dest_min, in[2]);
+          dest_max = MAX (in[0],  in[1]);
+          dest_max = MAX (dest_max, in[2]);
+          dest_l   = (dest_min + dest_max) / 2.0f;
+
+          src_min  = MIN (layer[0],  layer[1]);
+          src_min  = MIN (src_min, layer[2]);
+          src_max  = MAX (layer[0],  layer[1]);
+          src_max  = MAX (src_max, layer[2]);
+          src_l    = (src_min + src_max) / 2.0f;
+
+          if (fabs (src_l) > EPSILON && fabs (1.0 - src_l) > EPSILON)
+            {
+              gboolean dest_high;
+              gboolean src_high;
+              gfloat   ratio;
+              gfloat   offset;
+              gint     c;
+
+              dest_high = dest_l > 0.5f;
+              src_high  = src_l  > 0.5f;
+
+              dest_l = MIN (dest_l, 1.0f - dest_l);
+              src_l  = MIN (src_l,  1.0f - src_l);
+
+              ratio                  = dest_l / src_l;
+
+              offset                 = 0.0f;
+              if (dest_high) offset += 1.0f - 2.0f * dest_l;
+              if (src_high)  offset += 2.0f * dest_l - ratio;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = layer[c] * ratio + offset;
+            }
+          else
+            {
+              comp[RED]   = dest_l;
+              comp[GREEN] = dest_l;
+              comp[BLUE]  = dest_l;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hsv_hue (GeglOperation *operation,
+                                         const gfloat  *in,
+                                         const gfloat  *layer,
+                                         gfloat        *comp,
+                                         gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat src_min,  src_max,  src_delta;
+          gfloat dest_min, dest_max, dest_delta, dest_s;
+
+          src_min   = MIN (layer[0], layer[1]);
+          src_min   = MIN (src_min, layer[2]);
+          src_max   = MAX (layer[0], layer[1]);
+          src_max   = MAX (src_max, layer[2]);
+          src_delta = src_max - src_min;
+
+          if (src_delta > EPSILON)
+            {
+              gfloat ratio;
+              gfloat offset;
+              gint   c;
+
+              dest_min   = MIN (in[0], in[1]);
+              dest_min   = MIN (dest_min, in[2]);
+              dest_max   = MAX (in[0], in[1]);
+              dest_max   = MAX (dest_max, in[2]);
+              dest_delta = dest_max - dest_min;
+              dest_s     = dest_max ? dest_delta / dest_max : 0.0f;
+
+              ratio  = dest_s * dest_max / src_delta;
+              offset = dest_max - src_max * ratio;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = layer[c] * ratio + offset;
+            }
+          else
+            {
+              gint c;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = in[c];
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hsv_saturation (GeglOperation *operation,
+                                                const gfloat  *in,
+                                                const gfloat  *layer,
+                                                gfloat        *comp,
+                                                gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat src_min,  src_max,  src_delta, src_s;
+          gfloat dest_min, dest_max, dest_delta;
+
+          dest_min   = MIN (in[0], in[1]);
+          dest_min   = MIN (dest_min, in[2]);
+          dest_max   = MAX (in[0], in[1]);
+          dest_max   = MAX (dest_max, in[2]);
+          dest_delta = dest_max - dest_min;
+
+          if (dest_delta > EPSILON)
+            {
+              gfloat ratio;
+              gfloat offset;
+              gint   c;
+
+              src_min   = MIN (layer[0], layer[1]);
+              src_min   = MIN (src_min, layer[2]);
+              src_max   = MAX (layer[0], layer[1]);
+              src_max   = MAX (src_max, layer[2]);
+              src_delta = src_max - src_min;
+              src_s     = src_max ? src_delta / src_max : 0.0f;
+
+              ratio  = src_s * dest_max / dest_delta;
+              offset = (1.0f - ratio) * dest_max;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = in[c] * ratio + offset;
+            }
+          else
+            {
+              comp[RED]   = dest_max;
+              comp[GREEN] = dest_max;
+              comp[BLUE]  = dest_max;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_hsv_value (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat dest_v;
+          gfloat src_v;
+
+          dest_v = MAX (in[0], in[1]);
+          dest_v = MAX (dest_v, in[2]);
+
+          src_v  = MAX (layer[0], layer[1]);
+          src_v  = MAX (src_v, layer[2]);
+
+          if (fabs (dest_v) > EPSILON)
+            {
+              gfloat ratio = src_v / dest_v;
+              gint   c;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = in[c] * ratio;
+            }
+          else
+            {
+              comp[RED]   = src_v;
+              comp[GREEN] = src_v;
+              comp[BLUE]  = src_v;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_lch_chroma (GeglOperation *operation,
+                                            const gfloat  *in,
+                                            const gfloat  *layer,
+                                            gfloat        *comp,
+                                            gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat A1 = in[1];
+          gfloat B1 = in[2];
+          gfloat c1 = hypotf (A1, B1);
+
+          if (c1 > EPSILON)
+            {
+              gfloat A2 = layer[1];
+              gfloat B2 = layer[2];
+              gfloat c2 = hypotf (A2, B2);
+              gfloat A  = c2 * A1 / c1;
+              gfloat B  = c2 * B1 / c1;
+
+              comp[0] = in[0];
+              comp[1] = A;
+              comp[2] = B;
+            }
+          else
+            {
+              comp[0] = in[0];
+              comp[1] = in[1];
+              comp[2] = in[2];
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_lch_color (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          comp[0] = in[0];
+          comp[1] = layer[1];
+          comp[2] = layer[2];
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+  }
+}
+
+void
+gimp_operation_layer_mode_blend_lch_hue (GeglOperation *operation,
+                                         const gfloat  *in,
+                                         const gfloat  *layer,
+                                         gfloat        *comp,
+                                         gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat A2 = layer[1];
+          gfloat B2 = layer[2];
+          gfloat c2 = hypotf (A2, B2);
+
+          if (c2 > EPSILON)
+            {
+              gfloat A1 = in[1];
+              gfloat B1 = in[2];
+              gfloat c1 = hypotf (A1, B1);
+              gfloat A  = c1 * A2 / c2;
+              gfloat B  = c1 * B2 / c2;
+
+              comp[0] = in[0];
+              comp[1] = A;
+              comp[2] = B;
+            }
+          else
+            {
+              comp[0] = in[0];
+              comp[1] = in[1];
+              comp[2] = in[2];
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_lch_lightness (GeglOperation *operation,
+                                               const gfloat  *in,
+                                               const gfloat  *layer,
+                                               gfloat        *comp,
+                                               gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          comp[0] = layer[0];
+          comp[1] = in[1];
+          comp[2] = in[2];
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_lighten_only (GeglOperation *operation,
+                                              const gfloat  *in,
+                                              const gfloat  *layer,
+                                              gfloat        *comp,
+                                              gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = MAX (in[c], layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_linear_burn (GeglOperation *operation,
+                                             const gfloat  *in,
+                                             const gfloat  *layer,
+                                             gfloat        *comp,
+                                             gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] + layer[c] - 1.0f;
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+/* added according to:
+    http://www.deepskycolors.com/archivo/2010/04/21/formulas-for-Photoshop-blending-modes.html */
+void
+gimp_operation_layer_mode_blend_linear_light (GeglOperation *operation,
+                                              const gfloat  *in,
+                                              const gfloat  *layer,
+                                              gfloat        *comp,
+                                              gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat val;
+
+              if (layer[c] <= 0.5f)
+                val = in[c] + 2.0f * layer[c] - 1.0f;
+              else
+                val = in[c] + 2.0f * (layer[c] - 0.5f);
+
+              comp[c] = val;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_luma_darken_only (GeglOperation *operation,
+                                                  const gfloat  *in,
+                                                  const gfloat  *layer,
+                                                  gfloat        *comp,
+                                                  gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat dest_luminance;
+          gfloat src_luminance;
+          gint   c;
+
+          dest_luminance = GIMP_RGB_LUMINANCE (in[0],    in[1],    in[2]);
+          src_luminance  = GIMP_RGB_LUMINANCE (layer[0], layer[1], layer[2]);
+
+          if (dest_luminance <= src_luminance)
+            {
+              for (c = 0; c < 3; c++)
+                comp[c] = in[c];
+            }
+          else
+            {
+              for (c = 0; c < 3; c++)
+                comp[c] = layer[c];
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_luma_lighten_only (GeglOperation *operation,
+                                                   const gfloat  *in,
+                                                   const gfloat  *layer,
+                                                   gfloat        *comp,
+                                                   gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gfloat dest_luminance;
+          gfloat src_luminance;
+          gint   c;
+
+          dest_luminance = GIMP_RGB_LUMINANCE (in[0],    in[1],    in[2]);
+          src_luminance  = GIMP_RGB_LUMINANCE (layer[0], layer[1], layer[2]);
+
+          if (dest_luminance >= src_luminance)
+            {
+              for (c = 0; c < 3; c++)
+                comp[c] = in[c];
+            }
+          else
+            {
+              for (c = 0; c < 3; c++)
+                comp[c] = layer[c];
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_luminance (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  static const Babl *fish;
+  gfloat            *scratch;
+  gfloat            *in_Y;
+  gfloat            *layer_Y;
+
+  if (! fish)
+    fish = babl_fish ("RGBA float", "Y float");
+
+  scratch = gegl_scratch_new (gfloat, 2 * samples);
+
+  in_Y    = scratch;
+  layer_Y = scratch + samples;
+
+  babl_process (fish, in,    in_Y,    samples);
+  babl_process (fish, layer, layer_Y, samples);
+
+  while (samples--)
+    {
+      if (layer[ALPHA] != 0.0f && in[ALPHA] != 0.0f)
+        {
+          gfloat ratio = safe_div (layer_Y[0], in_Y[0]);
+          gint   c;
+
+          for (c = 0; c < 3; c ++)
+            comp[c] = in[c] * ratio;
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp    += 4;
+      in      += 4;
+      layer   += 4;
+      in_Y    ++;
+      layer_Y ++;
+    }
+
+  gegl_scratch_free (scratch);
+}
+
+void
+gimp_operation_layer_mode_blend_multiply (GeglOperation *operation,
+                                          const gfloat  *in,
+                                          const gfloat  *layer,
+                                          gfloat        *comp,
+                                          gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] * layer[c];
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_overlay (GeglOperation *operation,
+                                         const gfloat  *in,
+                                         const gfloat  *layer,
+                                         gfloat        *comp,
+                                         gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat val;
+
+              if (in[c] < 0.5f)
+                val = 2.0f * in[c] * layer[c];
+              else
+                val = 1.0f - 2.0f * (1.0f - layer[c]) * (1.0f - in[c]);
+
+              comp[c] = val;
+            }
+        }
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+/* added according to:
+    http://www.deepskycolors.com/archivo/2010/04/21/formulas-for-Photoshop-blending-modes.html */
+void
+gimp_operation_layer_mode_blend_pin_light (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat val;
+
+              if (layer[c] > 0.5f)
+                val = MAX(in[c], 2.0f * (layer[c] - 0.5f));
+              else
+                val = MIN(in[c], 2.0f * layer[c]);
+
+              comp[c] = val;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_screen (GeglOperation *operation,
+                                        const gfloat  *in,
+                                        const gfloat  *layer,
+                                        gfloat        *comp,
+                                        gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = 1.0f - (1.0f - in[c])   * (1.0f - layer[c]);
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_softlight (GeglOperation *operation,
+                                           const gfloat  *in,
+                                           const gfloat  *layer,
+                                           gfloat        *comp,
+                                           gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat multiply = in[c] * layer[c];
+              gfloat screen   = 1.0f - (1.0f - in[c]) * (1.0f - layer[c]);
+              gfloat val      = (1.0f - in[c]) * multiply + in[c] * screen;
+
+              comp[c] = val;
+            }
+        }
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+void
+gimp_operation_layer_mode_blend_subtract (GeglOperation *operation,
+                                          const gfloat  *in,
+                                          const gfloat  *layer,
+                                          gfloat        *comp,
+                                          gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            comp[c] = in[c] - layer[c];
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+/* added according to:
+    http://www.simplefilter.de/en/basics/mixmods.html */
+void
+gimp_operation_layer_mode_blend_vivid_light (GeglOperation *operation,
+                                             const gfloat  *in,
+                                             const gfloat  *layer,
+                                             gfloat        *comp,
+                                             gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          gint c;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat val;
+
+              if (layer[c] <= 0.5f)
+                {
+                  val = 1.0f - safe_div (1.0f - in[c], 2.0f * layer[c]);
+                  val = MAX (val, 0.0f);
+                }
+              else
+                {
+                  val = safe_div (in[c], 2.0f * (1.0f - layer[c]));
+                  val = MIN (val, 1.0f);
+                }
+
+              comp[c] = val;
+            }
+        }
+
+      comp[ALPHA] = layer[ALPHA];
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}
+
+
+/*  subtractive blending functions.  these functions must set comp[ALPHA] to
+ *  the modified alpha of the overlapping content, as a fraction of the
+ *  original overlapping content (i.e., an alpha of 1.0 specifies that no
+ *  content is subtracted.)  when in[ALPHA] or layer[ALPHA] are zero, the value
+ *  of comp[RED..BLUE] is unconstrained (in particular, it may be NaN).
+ */
+
+
+void
+gimp_operation_layer_mode_blend_color_erase (GeglOperation *operation,
+                                             const gfloat  *in,
+                                             const gfloat  *layer,
+                                             gfloat        *comp,
+                                             gint           samples)
+{
+  while (samples--)
+    {
+      if (in[ALPHA] != 0.0f && layer[ALPHA] != 0.0f)
+        {
+          const gfloat *color   = in;
+          const gfloat *bgcolor = layer;
+          gfloat       alpha;
+          gint         c;
+
+          alpha = 0.0f;
+
+          for (c = 0; c < 3; c++)
+            {
+              gfloat col   = CLAMP (color[c],   0.0f, 1.0f);
+              gfloat bgcol = CLAMP (bgcolor[c], 0.0f, 1.0f);
+
+              if (fabs (col - bgcol) > EPSILON)
+                {
+                  gfloat a;
+
+                  if (col > bgcol)
+                    a = (col - bgcol) / (1.0f - bgcol);
+                  else
+                    a = (bgcol - col) / bgcol;
+
+                  alpha = MAX (alpha, a);
+                }
+            }
+
+          if (alpha > EPSILON)
+            {
+              gfloat alpha_inv = 1.0f / alpha;
+
+              for (c = 0; c < 3; c++)
+                comp[c] = (color[c] - bgcolor[c]) * alpha_inv + bgcolor[c];
+            }
+          else
+            {
+              comp[RED] = comp[GREEN] = comp[BLUE] = 0.0f;
+            }
+
+          comp[ALPHA] = alpha;
+        }
+      else
+        comp[ALPHA] = 0.0f;
+
+      comp  += 4;
+      layer += 4;
+      in    += 4;
+    }
+}