[gimp] modules: add a filmic proof display filter

[Øyvind "pippin" Kolås <ok src gnome org>]

commit fe14feaaff93afbffa2d49ff2dc0484f31e2e935
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue Jul 17 15:57:34 2018 +0200

    modules: add a filmic proof display filter
    
    Add a display filter that can be used in scene-referred imaging workflows,
    this is using a luminance-only approximation of the ACES filmic HDR to SDR
    proofing mapping - see link in source comment for details.

 modules/Makefile.am             |   6 ++
 modules/display-filter-filmic.c | 231 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 237 insertions(+)
---
diff --git a/modules/Makefile.am b/modules/Makefile.am
index 867fb6d61a..e86fa35f9f 100644
--- a/modules/Makefile.am
+++ b/modules/Makefile.am
@@ -37,6 +37,7 @@ lib_LTLIBRARIES = \
        libcolor-selector-wheel.la              \
        libdisplay-filter-clip-warning.la       \
        libdisplay-filter-color-blind.la        \
+       libdisplay-filter-filmic.la             \
        libdisplay-filter-gamma.la              \
        libdisplay-filter-high-contrast.la      \
        $(controller_midi_module)               \
@@ -70,6 +71,11 @@ libdisplay_filter_color_blind_la_SOURCES = display-filter-color-blind.c
 libdisplay_filter_color_blind_la_LDFLAGS = -avoid-version -module $(no_undefined)
 libdisplay_filter_color_blind_la_LIBADD = $(display_filter_libadd)
 
+
+libdisplay_filter_filmic_la_SOURCES = display-filter-filmic.c
+libdisplay_filter_filmic_la_LDFLAGS = -avoid-version -module $(no_undefined)
+libdisplay_filter_filmic_la_LIBADD = $(display_filter_libadd)
+
 libdisplay_filter_gamma_la_SOURCES = display-filter-gamma.c
 libdisplay_filter_gamma_la_LDFLAGS = -avoid-version -module $(no_undefined)
 libdisplay_filter_gamma_la_LIBADD = $(display_filter_libadd)
diff --git a/modules/display-filter-filmic.c b/modules/display-filter-filmic.c
new file mode 100644
index 0000000000..56fa757f12
--- /dev/null
+++ b/modules/display-filter-filmic.c
@@ -0,0 +1,231 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 2018 Øyvind Kolås <pippin 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 <gegl.h>
+#include <gtk/gtk.h>
+
+#include "libgimpcolor/gimpcolor.h"
+#include "libgimpconfig/gimpconfig.h"
+#include "libgimpmath/gimpmath.h"
+#include "libgimpmodule/gimpmodule.h"
+#include "libgimpwidgets/gimpwidgets.h"
+
+#include "libgimp/libgimp-intl.h"
+
+#define DEFAULT_EXPOSURE 0.0
+
+#define CDISPLAY_TYPE_FILMIC            (cdisplay_filmic_get_type ())
+#define CDISPLAY_FILMIC(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), CDISPLAY_TYPE_FILMIC, 
CdisplayFilmic))
+#define CDISPLAY_FILMIC_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass), CDISPLAY_TYPE_FILMIC, 
CdisplayFilmicClass))
+#define CDISPLAY_IS_FILMIC(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), CDISPLAY_TYPE_FILMIC))
+#define CDISPLAY_IS_FILMIC_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), CDISPLAY_TYPE_FILMIC))
+
+
+typedef struct _CdisplayFilmic      CdisplayFilmic;
+typedef struct _CdisplayFilmicClass CdisplayFilmicClass;
+
+struct _CdisplayFilmic
+{
+  GimpColorDisplay  parent_instance;
+
+  gdouble           exposure;
+};
+
+struct _CdisplayFilmicClass
+{
+  GimpColorDisplayClass  parent_instance;
+};
+
+
+enum
+{
+  PROP_0,
+  PROP_EXPOSURE
+};
+
+
+static GType       cdisplay_filmic_get_type        (void);
+
+static void        cdisplay_filmic_set_property    (GObject            *object,
+                                                   guint               property_id,
+                                                   const GValue       *value,
+                                                   GParamSpec         *pspec);
+static void        cdisplay_filmic_get_property    (GObject            *object,
+                                                   guint               property_id,
+                                                   GValue             *value,
+                                                   GParamSpec         *pspec);
+
+static void        cdisplay_filmic_convert_buffer  (GimpColorDisplay   *display,
+                                                   GeglBuffer         *buffer,
+                                                   GeglRectangle      *area);
+static void        cdisplay_filmic_set_exposure    (CdisplayFilmic      *filmic,
+                                                   gdouble             value);
+
+
+static const GimpModuleInfo cdisplay_filmic_info =
+{
+  GIMP_MODULE_ABI_VERSION,
+  N_("Filmic HDR to SDR proof color display filter, usin an approximation of the ACES filmic transform."),
+  "Øyvind Kolås <pippin gimp org>",
+  "v0.2",
+  "(c) 2018, released under the GPL",
+  "July 17, 2018"
+};
+
+
+G_DEFINE_DYNAMIC_TYPE (CdisplayFilmic, cdisplay_filmic,
+                       GIMP_TYPE_COLOR_DISPLAY)
+
+
+G_MODULE_EXPORT const GimpModuleInfo *
+gimp_module_query (GTypeModule *module)
+{
+  return &cdisplay_filmic_info;
+}
+
+G_MODULE_EXPORT gboolean
+gimp_module_register (GTypeModule *module)
+{
+  cdisplay_filmic_register_type (module);
+
+  return TRUE;
+}
+
+static void
+cdisplay_filmic_class_init (CdisplayFilmicClass *klass)
+{
+  GObjectClass          *object_class  = G_OBJECT_CLASS (klass);
+  GimpColorDisplayClass *display_class = GIMP_COLOR_DISPLAY_CLASS (klass);
+
+  object_class->get_property     = cdisplay_filmic_get_property;
+  object_class->set_property     = cdisplay_filmic_set_property;
+
+  GIMP_CONFIG_PROP_DOUBLE (object_class, PROP_EXPOSURE,
+                           "exposure",
+                           _("pre-transform change in stops"),
+                           NULL,
+                           -10.0, 10.0, DEFAULT_EXPOSURE,
+                           1);
+
+  display_class->name            = _("Filmic");
+  display_class->help_id         = "gimp-colordisplay-filmic";
+  display_class->icon_name       = GIMP_ICON_DISPLAY_FILTER_GAMMA;
+
+  display_class->convert_buffer  = cdisplay_filmic_convert_buffer;
+}
+
+static void
+cdisplay_filmic_class_finalize (CdisplayFilmicClass *klass)
+{
+}
+
+static void
+cdisplay_filmic_init (CdisplayFilmic *filmic)
+{
+}
+
+static void
+cdisplay_filmic_get_property (GObject    *object,
+                             guint       property_id,
+                             GValue     *value,
+                             GParamSpec *pspec)
+{
+  CdisplayFilmic *filmic = CDISPLAY_FILMIC (object);
+
+  switch (property_id)
+    {
+    case PROP_EXPOSURE:
+      g_value_set_double (value, filmic->exposure);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+cdisplay_filmic_set_property (GObject      *object,
+                             guint         property_id,
+                             const GValue *value,
+                             GParamSpec   *pspec)
+{
+  CdisplayFilmic *filmic = CDISPLAY_FILMIC (object);
+
+  switch (property_id)
+    {
+    case PROP_EXPOSURE:
+      cdisplay_filmic_set_exposure (filmic, g_value_get_double (value));
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static inline float aces_filmic (float x)
+{
+ /*
+    Approximation of the ACES filmic HDR to SDR mapping from:
+    https://github.com/TheRealMJP/BakingLab/blob/master/BakingLab/ACES.hlsl
+  */
+ float a = x * (x + 0.0245786f) - 0.000090537f;
+ float b = x * (0.983729f * x + 0.4329510f) + 0.238081f;
+ return a / b;
+}
+
+static void
+cdisplay_filmic_convert_buffer (GimpColorDisplay *display,
+                               GeglBuffer       *buffer,
+                               GeglRectangle    *area)
+{
+  CdisplayFilmic     *filter = CDISPLAY_FILMIC (display);
+  GeglBufferIterator *iter;
+  float gain = 1.0f / exp2f(-filter->exposure);
+
+  iter = gegl_buffer_iterator_new (buffer, area, 0,
+                                   babl_format ("RGBA float"),
+                                   GEGL_ACCESS_READWRITE, GEGL_ABYSS_NONE);
+
+  while (gegl_buffer_iterator_next (iter))
+    {
+      gfloat *data  = iter->data[0];
+      gint    count = iter->length;
+
+      while (count--)
+        {
+          *data = aces_filmic (*data * gain); data++;
+          *data = aces_filmic (*data * gain); data++;
+          *data = aces_filmic (*data * gain); data++;
+          data++;
+        }
+    }
+}
+
+static void
+cdisplay_filmic_set_exposure (CdisplayFilmic *filmic,
+                              gdouble        value)
+{
+  if (value != filmic->exposure)
+    {
+      filmic->exposure = value;
+
+      g_object_notify (G_OBJECT (filmic), "exposure");
+      gimp_color_display_changed (GIMP_COLOR_DISPLAY (filmic));
+    }
+}