[gnome-photos/gnome-3-22] base-item: Make the previews faster by downscaling the image earlier

[Debarshi Ray <debarshir src gnome org>]

commit a8abaf0a9f4941429859f597e71e4f5e6d24d7a5
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Jan 25 17:10:57 2017 +0100

    base-item: Make the previews faster by downscaling the image earlier
    
    Smaller the number of pixels, the faster the pixel crunching is going
    to be. Therefore let's downscale the image before we run the operation.

 src/photos-base-item.c |   32 +++++++++++++++++++++++++-------
 1 files changed, 25 insertions(+), 7 deletions(-)
---
diff --git a/src/photos-base-item.c b/src/photos-base-item.c
index d1a9edc..2773be2 100644
--- a/src/photos-base-item.c
+++ b/src/photos-base-item.c
@@ -2470,6 +2470,7 @@ photos_base_item_create_preview (PhotosBaseItem *self,
   const Babl *format;
   GeglBuffer *buffer_cropped = NULL;
   GeglBuffer *buffer_orig = NULL;
+  GeglBuffer *buffer_scaled = NULL;
   GeglBuffer *buffer = NULL;
   GeglNode *buffer_source;
   GeglNode *graph = NULL;
@@ -2481,6 +2482,7 @@ photos_base_item_create_preview (PhotosBaseItem *self,
   static const cairo_user_data_key_t key;
   const gchar *name;
   gdouble zoom;
+  gint bpp;
   gint min_dimension;
   gint size_scaled;
   gint stride;
@@ -2522,8 +2524,28 @@ photos_base_item_create_preview (PhotosBaseItem *self,
   bbox.y = y;
   buffer_cropped = gegl_buffer_create_sub_buffer (buffer, &bbox);
 
+  roi.height = size_scaled;
+  roi.width = size_scaled;
+  roi.x = (gint) ((gdouble) x * zoom + 0.5);
+  roi.y = (gint) ((gdouble) y * zoom + 0.5);
+
+  format = gegl_buffer_get_format (buffer_cropped);
+  bpp = babl_format_get_bytes_per_pixel (format);
+  buf = g_malloc0_n (roi.height * roi.width, bpp);
+
+  start = g_get_monotonic_time ();
+
+  gegl_buffer_get (buffer_cropped, &roi, zoom, format, buf, GEGL_AUTO_ROWSTRIDE, GEGL_ABYSS_NONE);
+
+  end = g_get_monotonic_time ();
+  photos_debug (PHOTOS_DEBUG_GEGL, "Create Preview: Downscale: %" G_GINT64_FORMAT, end - start);
+
+  roi.x = 0;
+  roi.y = 0;
+  buffer_scaled = gegl_buffer_linear_new_from_data (buf, format, &roi, GEGL_AUTO_ROWSTRIDE, g_free, NULL);
+
   graph = gegl_node_new ();
-  buffer_source = gegl_node_new_child (graph, "operation", "gegl:buffer-source", "buffer", buffer_cropped, 
NULL);
+  buffer_source = gegl_node_new_child (graph, "operation", "gegl:buffer-source", "buffer", buffer_scaled, 
NULL);
 
   operation_node = gegl_node_new_child (graph, "operation", operation, NULL);
 
@@ -2540,18 +2562,13 @@ photos_base_item_create_preview (PhotosBaseItem *self,
   end = g_get_monotonic_time ();
   photos_debug (PHOTOS_DEBUG_GEGL, "Create Preview: Process: %" G_GINT64_FORMAT, end - start);
 
-  roi.height = size_scaled;
-  roi.width = size_scaled;
-  roi.x = (gint) ((gdouble) x * zoom + 0.5);
-  roi.y = (gint) ((gdouble) y * zoom + 0.5);
-
   stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, roi.width);
   buf = g_malloc0 (stride * roi.height);
   format = babl_format ("cairo-ARGB32");
 
   start = g_get_monotonic_time ();
 
-  gegl_node_blit (operation_node, zoom, &roi, format, buf, GEGL_AUTO_ROWSTRIDE, GEGL_BLIT_DEFAULT);
+  gegl_node_blit (operation_node, 1.0, &roi, format, buf, GEGL_AUTO_ROWSTRIDE, GEGL_BLIT_DEFAULT);
 
   end = g_get_monotonic_time ();
   photos_debug (PHOTOS_DEBUG_GEGL, "Create Preview: Node Blit: %" G_GINT64_FORMAT, end - start);
@@ -2563,6 +2580,7 @@ photos_base_item_create_preview (PhotosBaseItem *self,
   g_object_unref (buffer);
   g_object_unref (buffer_cropped);
   g_object_unref (buffer_orig);
+  g_object_unref (buffer_scaled);
   g_object_unref (graph);
 
   return surface;