[gthumb] use a faster filter if the image is big

[Paolo Bacchilega <paobac src gnome org>]

commit 63eeb56356eaf10a233312943be67e08fe82e4de
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sun Jun 30 10:26:49 2013 +0200

    use a faster filter if the image is big

 gthumb/gth-image-dragger.c |   23 ++++++++++++++++++-----
 1 files changed, 18 insertions(+), 5 deletions(-)
---
diff --git a/gthumb/gth-image-dragger.c b/gthumb/gth-image-dragger.c
index 9b6d8eb..0b3fe27 100644
--- a/gthumb/gth-image-dragger.c
+++ b/gthumb/gth-image-dragger.c
@@ -28,6 +28,9 @@
 #include "pixbuf-utils.h"
 
 
+#define SIZE_TOO_BIG_FOR_SCALE_BILINEAR (3000 * 3000)
+
+
 struct _GthImageDraggerPrivate {
        GthImageViewer  *viewer;
        gboolean         draggable;
@@ -310,6 +313,7 @@ typedef struct {
        int              new_width;
        int              new_height;
        cairo_surface_t *scaled;
+       scale_filter_t   filter;
 } ScaleData;
 
 
@@ -333,7 +337,7 @@ _gth_image_dragger_scale_exec (GthAsyncTask *task,
        scale_data->scaled = _cairo_image_surface_scale (scale_data->image,
                                                         scale_data->new_width,
                                                         scale_data->new_height,
-                                                        SCALE_FILTER_GOOD,
+                                                        scale_data->filter,
                                                         task);
 
        return NULL;
@@ -367,7 +371,8 @@ static void
 _gth_image_dragger_create_scaled_high_quality (GthImageDragger *self,
                                               cairo_surface_t *image,
                                               int              new_width,
-                                              int              new_height)
+                                              int              new_height,
+                                              scale_filter_t   filter)
 {
        ScaleData *scale_data;
 
@@ -380,6 +385,7 @@ _gth_image_dragger_create_scaled_high_quality (GthImageDragger *self,
        scale_data->new_width = new_width;
        scale_data->new_height = new_height;
        scale_data->scaled = NULL;
+       scale_data->filter = filter;
 
        self->priv->scale_task = gth_async_task_new (NULL,
                                                     _gth_image_dragger_scale_exec,
@@ -399,6 +405,7 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
        int              original_width, original_height;
        double           zoom;
        int              new_width, new_height;
+       scale_filter_t   filter;
 
        if (self->priv->scale_task != NULL) {
                gth_task_cancel (self->priv->scale_task);
@@ -434,10 +441,16 @@ _gth_image_dragger_update_scaled_image (GthImageDragger *self)
        new_width = zoom * image_width;
        new_height = zoom * image_height;
 
-       /*self->priv->scaled = _cairo_image_surface_scale_nearest (image, new_width, new_height);*/
-       self->priv->scaled = _cairo_image_surface_scale_bilinear (image, new_width, new_height);
+       if (image_width * image_height > SIZE_TOO_BIG_FOR_SCALE_BILINEAR) {
+               self->priv->scaled = _cairo_image_surface_scale_nearest (image, new_width, new_height);
+               filter = SCALE_FILTER_BOX;
+       }
+       else {
+               self->priv->scaled = _cairo_image_surface_scale_bilinear (image, new_width, new_height);
+               filter = SCALE_FILTER_TRIANGLE;
+       }
 
-       _gth_image_dragger_create_scaled_high_quality (self, image, new_width, new_height);
+       _gth_image_dragger_create_scaled_high_quality (self, image, new_width, new_height, filter);
 }