[gegl] operations/workshop: Allow to specify "srgb" for operating in gamma-encoded space

[Jon Nordby <jonnor src gnome org>]

commit d7515aa4b05c68da3354e2725ab06ecd16768c2b
Author: Jon Nordby <jononor gmail com>
Date:   Thu Aug 14 01:18:26 2014 +0200

    operations/workshop: Allow to specify "srgb" for operating in gamma-encoded space
    
    This is usually what people expect coming from PS etc.
    Also moves the gradient calculation logic into prepare(),
    as that is guaranteed to be called on all property changes.
    Could maybe even drop it, as most changes will invalidate cache...

 operations/workshop/gradient-map.c |   63 +++++++++++++++++++-----------------
 1 files changed, 33 insertions(+), 30 deletions(-)
---
diff --git a/operations/workshop/gradient-map.c b/operations/workshop/gradient-map.c
index 0eec323..ae8263b 100644
--- a/operations/workshop/gradient-map.c
+++ b/operations/workshop/gradient-map.c
@@ -33,6 +33,7 @@ property_color(color4, _("Color 4"), "white")
 property_double(stop4, _("Stop 4"), 1.0)
 property_color(color5, _("Color 5"), "white")
 property_double(stop5, _("Stop 5"), 1.0)
+property_boolean(srgb, _("sRGB"), FALSE)
 #else
 
 #define GEGL_OP_POINT_FILTER
@@ -47,6 +48,8 @@ property_double(stop5, _("Stop 5"), 1.0)
 // - should be deserializable from a (JSON) array of GeglColor values
 
 #define GRADIENT_STOPS 5
+static const gint gradient_length = 2048;
+static const gint gradient_channels = 4; // RGBA
 
 typedef struct RgbaColor_ {
     gdouble r;
@@ -86,9 +89,9 @@ mapf(float x, float in_min, float in_max, float out_min, float out_max)
 
 static gdouble *
 create_linear_gradient(GeglColor **colors, gdouble *stops, const gint no_stops,
-                       const gint gradient_len, gint gradient_channels)
+                       const gint gradient_len, gint channels)
 {
-    gdouble *samples = (gdouble *)g_new(gdouble, gradient_len*gradient_channels);
+    gdouble *samples = (gdouble *)g_new(gdouble, gradient_len*channels);
 
     // XXX: assumes that
     // - stops are in ascending order
@@ -111,7 +114,7 @@ create_linear_gradient(GeglColor **colors, gdouble *stops, const gint no_stops,
         }
         const float from_pos = (from_stop < 0) ? 0.0 : stops[from_stop];
         const float weight = ((to_stop-from_stop) == 0) ? 1.0 : mapf(pos, from_pos, to_pos, 0.0, 1.0);
-        const size_t offset = px*gradient_channels;
+        const size_t offset = px*channels;
         pixel_interpolate_gradient(samples, offset, &from, &to, weight);
     }
     return samples;
@@ -171,8 +174,24 @@ static void prepare (GeglOperation *operation)
 {
   GeglProperties *o = GEGL_PROPERTIES (operation);
   GradientMapProperties *props = (GradientMapProperties*)o->user_data;
+  GeglColor *colors[GRADIENT_STOPS] = {
+      o->color1,
+      o->color2,
+      o->color3,
+      o->color4,
+      o->color5
+  };
+  gdouble stops[GRADIENT_STOPS] = {
+      o->stop1,
+      o->stop2,
+      o->stop3,
+      o->stop4,
+      o->stop5
+  };
+  const Babl *f = (o->srgb) ? babl_format ("Y'A float") : babl_format ("YA float");
+  gboolean cached = FALSE;
 
-  gegl_operation_set_format (operation, "input", babl_format ("YA float"));
+  gegl_operation_set_format (operation, "input", f);
   gegl_operation_set_format (operation, "output", babl_format ("RGBA float"));
 
   if (!props)
@@ -181,6 +200,16 @@ static void prepare (GeglOperation *operation)
       props->gradient = NULL;
       o->user_data = props;
     }
+
+  cached = gradient_is_cached(props->gradient, colors, stops, GRADIENT_STOPS,
+                              props->cached_colors, props->cached_stops);
+  if (!cached) {
+    if (props->gradient) {
+        g_free(props->gradient);
+    }
+    props->gradient = create_linear_gradient(colors, stops, GRADIENT_STOPS, gradient_length, 
gradient_channels);
+    update_cached_vars(colors, GRADIENT_STOPS, props->cached_colors, stops, props->cached_stops);
+  }
 }
 
 static void finalize (GObject *object)
@@ -209,33 +238,7 @@ process (GeglOperation       *op,
   GeglProperties *o = GEGL_PROPERTIES (op);
   gfloat     * GEGL_ALIGNED in_pixel = in_buf;
   gfloat     * GEGL_ALIGNED out_pixel = out_buf;
-  const gint gradient_length = 2048;
-  const gint gradient_channels = 4; // RGBA
   GradientMapProperties *props = (GradientMapProperties*)o->user_data;
-  GeglColor *colors[GRADIENT_STOPS] = {
-      o->color1,
-      o->color2,
-      o->color3,
-      o->color4,
-      o->color5
-  };
-  gdouble stops[GRADIENT_STOPS] = {
-      o->stop1,
-      o->stop2,
-      o->stop3,
-      o->stop4,
-      o->stop5
-  };
-
-  const gboolean cached = gradient_is_cached(props->gradient, colors, stops, GRADIENT_STOPS,
-                                       props->cached_colors, props->cached_stops);
-  if (!cached) {
-    if (props->gradient) {
-        g_free(props->gradient);
-    }
-    props->gradient = create_linear_gradient(colors, stops, GRADIENT_STOPS, gradient_length, 
gradient_channels);
-    update_cached_vars(colors, GRADIENT_STOPS, props->cached_colors, stops, props->cached_stops);
-  }
 
   for (int i=0; i<n_pixels; i++)
     {