Add a check box for gamma aware scaling

This is a hack because just changing the format doesn't work when the
image has an alpha channel

4 files changed, 52 insertions, 3 deletions

diff --git a/demos/scale.c b/demos/scale.c
index c872139d..4ced07ed 100644
--- a/demos/scale.c
+++ b/demos/scale.c
@@ -203,11 +203,25 @@ to_scale (double v)
     return pow (1.15, v);
 }
 
+static pixman_format_code_t
+get_format (app_t *app)
+{
+    /* FIXME: Just changing the format isn't correct when
+     * the image has an alpha channel since in that case we
+     * need to do a gamma aware premultiplication.
+     */
+    return gtk_toggle_button_get_active (
+	GTK_TOGGLE_BUTTON (
+	    get_widget (app, "gamma_checkbutton")))?
+	PIXMAN_a8r8g8b8_sRGB : PIXMAN_a8r8g8b8;
+}
+
 static void
 rescale (GtkWidget *may_be_null, app_t *app)
 {
     pixman_f_transform_t ftransform;
     pixman_transform_t transform;
+    pixman_format_code_t format;
     double new_width, new_height;
     double fscale_x, fscale_y;
     double rotation;
@@ -249,6 +263,8 @@ rescale (GtkWidget *may_be_null, app_t *app)
     pixman_transform_from_pixman_f_transform (&transform, &ftransform);
     pixman_image_set_transform (app->original, &transform);
 
+    pixman_image_set_format (app->original, get_format (app));
+
     params = pixman_filter_create_separable_convolution (
         &n_params,
         sx * 65536.0 + 0.5,
@@ -286,10 +302,11 @@ on_expose (GtkWidget *da, GdkEvent *event, gpointer data)
     pixman_image_t *tmp;
     cairo_t *cr;
     uint32_t *pixels;
+    pixman_format_code_t format;
 
     pixels = calloc (1, area->width * area->height * 4);
     tmp = pixman_image_create_bits (
-        PIXMAN_a8r8g8b8_sRGB, area->width, area->height, pixels, area->width * 4);
+        get_format (app), area->width, area->height, pixels, area->width * 4);
 
     if (area->x < app->scaled_width && area->y < app->scaled_height)
     {
@@ -414,6 +431,10 @@ app_new (pixman_image_t *original)
 	gtk_builder_get_object (app->builder, "lock_checkbutton"),
 	"toggled", G_CALLBACK (rescale), app);
     
+    g_signal_connect (
+	gtk_builder_get_object (app->builder, "gamma_checkbutton"),
+	"toggled", G_CALLBACK (rescale), app);
+    
     rescale (NULL, app);
     
     return app;
@@ -434,7 +455,7 @@ main (int argc, char **argv)
 	return -1;
     }
 
-    if (!(image = pixman_image_from_file (argv[1], PIXMAN_a8r8g8b8_sRGB)))
+    if (!(image = pixman_image_from_file (argv[1], PIXMAN_a8r8g8b8)))
     {
 	printf ("Could not load image \"%s\"\n", argv[1]);
 	return -1;
diff --git a/demos/scale.ui b/demos/scale.ui
index d498d26e..ee8773ee 100644
--- a/demos/scale.ui
+++ b/demos/scale.ui
@@ -186,6 +186,19 @@
                     <property name="position">1</property>
                   </packing>
 		</child>
+		<child>
+		  <object class="GtkCheckButton"
+			  id="gamma_checkbutton">
+		    <property name="label" translatable="yes">Gamma Aware</property>
+		    <property name="xalign">0.0</property>
+		  </object>
+                  <packing>
+                    <property name="expand">False</property>
+                    <property name="fill">False</property>
+                    <property name="padding">6</property>
+                    <property name="position">2</property>
+                  </packing>
+		</child>
                 <child>
                   <object class="GtkTable" id="grid1">
                     <property name="visible">True</property>
@@ -313,7 +326,7 @@
                   <packing>
                     <property name="expand">False</property>
                     <property name="padding">6</property>
-                    <property name="position">1</property>
+                    <property name="position">2</property>
                   </packing>
                 </child>
               </object>
diff --git a/pixman/pixman-image.c b/pixman/pixman-image.c
index 681864eb..3424f189 100644
--- a/pixman/pixman-image.c
+++ b/pixman/pixman-image.c
@@ -565,6 +565,17 @@ _pixman_image_validate (pixman_image_t *image)
 	_pixman_image_validate ((pixman_image_t *)image->common.alpha_map);
 }
 
+PIXMAN_EXPORT void
+pixman_image_set_format (pixman_image_t *image,
+			 pixman_format_code_t format)
+{
+    return_if_fail (image && image->type == BITS);
+
+    image->bits.format = format;
+
+    image_property_changed (image);
+}
+
 PIXMAN_EXPORT pixman_bool_t
 pixman_image_set_clip_region32 (pixman_image_t *   image,
                                 pixman_region32_t *region)
diff --git a/pixman/pixman-private.h b/pixman/pixman-private.h
index e246af04..4b64bb7b 100644
--- a/pixman/pixman-private.h
+++ b/pixman/pixman-private.h
@@ -320,6 +320,10 @@ void
 _pixman_image_reset_clip_region (pixman_image_t *image);
 
 void
+_pixman_image_set_format (pixman_image_t *image,
+			  pixman_format_code_t format);
+
+void
 _pixman_image_validate (pixman_image_t *image);
 
 #define PIXMAN_IMAGE_GET_LINE(image, x, y, type, out_stride, line, mul)	\