[gthumb] use the SCALE_FILTER_BOX filter to scale thumbails

[Paolo Bacchilega <paobac src gnome org>]

commit 8a38213a8e8ce23b404cd945ed586a3ee9fbbfb5
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Mon Jun 24 21:56:55 2013 +0200

    use the SCALE_FILTER_BOX filter to scale thumbails
    
    the box filter is fast and gives good quality when scaling big images to
    thumbnails.

 gthumb/gth-thumb-loader.c |   28 +++++++++++++++++++---------
 1 files changed, 19 insertions(+), 9 deletions(-)
---
diff --git a/gthumb/gth-thumb-loader.c b/gthumb/gth-thumb-loader.c
index e8638c7..63d7ef2 100644
--- a/gthumb/gth-thumb-loader.c
+++ b/gthumb/gth-thumb-loader.c
@@ -29,6 +29,7 @@
 #define GDK_PIXBUF_ENABLE_BACKEND
 #include <gtk/gtk.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
+#include "cairo-scale.h"
 #include "cairo-utils.h"
 #include "gio-utils.h"
 #include "glib-utils.h"
@@ -419,6 +420,15 @@ normalize_thumb (int *width,
 }
 
 
+static cairo_surface_t *
+_cairo_image_surface_scale_for_thumbnail (cairo_surface_t *image,
+                                         int              new_width,
+                                         int              new_height)
+{
+       return _cairo_image_surface_scale (image, new_width, new_height, SCALE_FILTER_BOX, NULL);
+}
+
+
 static void
 cache_image_ready_cb (GObject      *source_object,
                      GAsyncResult *res,
@@ -468,9 +478,9 @@ cache_image_ready_cb (GObject      *source_object,
                                    self->priv->requested_size,
                                    self->priv->cache_max_size);
        if (modified) {
-               GdkPixbuf *tmp = pixbuf;
-               pixbuf = _gdk_pixbuf_scale_simple_safe (tmp, width, height, GDK_INTERP_BILINEAR);
-               g_object_unref (tmp);
+               cairo_surface_t *tmp = surface;
+               surface = _cairo_image_surface_scale_for_thumbnail (tmp, width, height);
+               cairo_surface_destroy (tmp);
        }
 
        load_result = g_new0 (LoadResult, 1);
@@ -572,9 +582,9 @@ original_image_loaded_correctly (GthThumbLoader *self,
                                                self->priv->cache_max_size,
                                                FALSE);
                if (modified) {
-                       GdkPixbuf *tmp = local_pixbuf;
-                       local_pixbuf = _gdk_pixbuf_scale_simple_safe (tmp, width, height, 
GDK_INTERP_BILINEAR);
-                       g_object_unref (tmp);
+                       cairo_surface_t *tmp = local_image;
+                       local_image = _cairo_image_surface_scale_for_thumbnail (tmp, width, height);
+                       cairo_surface_destroy (tmp);
                }
 
                _gth_thumb_loader_save_to_cache (self, load_data->file_data, local_image);
@@ -587,9 +597,9 @@ original_image_loaded_correctly (GthThumbLoader *self,
                                    self->priv->requested_size,
                                    self->priv->cache_max_size);
        if (modified) {
-               GdkPixbuf *tmp = local_pixbuf;
-               local_pixbuf = _gdk_pixbuf_scale_simple_safe (tmp, width, height, GDK_INTERP_BILINEAR);
-               g_object_unref (tmp);
+               cairo_surface_t *tmp = local_image;
+               local_image = _cairo_image_surface_scale_for_thumbnail (tmp, width, height);
+               cairo_surface_destroy (tmp);
        }
 
        load_result = g_new0 (LoadResult, 1);