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

[Debarshi Ray <debarshir src gnome org>]

commit 22090a9dd9a04bfd6a46f9a57eb4e09b31eed660
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 3ca3d70..89e17eb 100644
--- a/src/photos-base-item.c
+++ b/src/photos-base-item.c
@@ -2564,6 +2564,7 @@ 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;
@@ -2575,6 +2576,7 @@ 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;
@@ -2616,8 +2618,28 @@ 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);
 
@@ -2634,18 +2656,13 @@ 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);
@@ -2657,6 +2674,7 @@ 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;