[gnome-photos/wip/rishi/faster-previews: 3/3] base-item: Downscale the image before running the preview operation

[Debarshi Ray <debarshir src gnome org>]

commit 69a74041612a2af71cb9101d8b9703bac28df466
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Jan 25 17:10:57 2017 +0100

    base-item: Downscale the image before running the preview operation
    
    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;