Add support for HiDPI images

This works by creating corresponding hidpi image sizes on startup and
letting the machinery generate high resolution images from the source
images (no way to use supplied images). However since browsers expect
exact image dimension multiples for the particular scale factor,
a reference image size (scale factor 1.0x) must be read first, then
cropped to match reference aspect ratio and resized to exact dimensions.
That way pixel-perfect results can be achieved for the chosen scale
factor.

TODO: the CSS background-image: image-set() tags are not supported
on Firefox.
TODO: try the 1.5x scale factor

1 files changed, 69 insertions, 1 deletions

diff --git a/src/setup.c b/src/setup.c
index 9780807..cf23044 100644
--- a/src/setup.c
+++ b/src/setup.c
@@ -155,6 +155,35 @@ image_sizes_compare_func (TImageSize *a, TImageSize *b)
   return sa - sb;
 }
 
+static gdouble *
+parse_hidpi_sizes (const gchar *s)
+{
+  gchar **split;
+  GArray *arr;
+  gchar *s2;
+  int i;
+  gdouble f;
+
+  if (! s || strlen (s) == 0)
+    return NULL;
+
+  arr = g_array_new (TRUE, TRUE, sizeof (gdouble));
+  split = g_strsplit (s, ",", -1);
+
+  for (i = 0; split[i] != NULL; i++) {
+    s2 = g_strstrip (split[i]);
+    if (s2[strlen(s2) - 1] != 'x')
+      continue;
+    s2[strlen(s2) - 1] = '\0';
+    f = g_ascii_strtod (s2, NULL);
+    g_array_append_val (arr, f);
+  }
+  g_strfreev (split);
+
+  return (gdouble *) g_array_free (arr, FALSE);
+}
+
+
 /*
  *   parse_design_setup_xml: XML parser for design.xml file
  */
@@ -166,7 +195,7 @@ parse_design_setup_xml (const gchar *filename)
   gchar *s2;
   gchar *s3;
   TGalleryDesign *design;
-  TImageSize *image_size;
+  TImageSize *image_size, *hidpi_image_size;
   TGalleryDesignTheme *theme;
   int count, c;
   int i, j;
@@ -202,6 +231,17 @@ parse_design_setup_xml (const gchar *filename)
   }
 
 
+  /*  hidpi section  */
+  if (xml_file_get_node_attribute_boolean_with_default (xml, "/design_setup/hidpi", "enabled", FALSE)) {
+    design->hidpi_upscale_threshold = xml_file_get_node_attribute_long_with_default (xml, "/design_setup/hidpi/threshold", "upscale", DEFAULT_UPSCALE_THRESHOLD);
+    s = xml_file_get_node_value (xml, "/design_setup/hidpi/sizes/text()");
+    design->hidpi_sizes = parse_hidpi_sizes (s);
+    g_free (s);
+    design->hidpi_quality = xml_file_get_node_attribute_long_with_default (xml, "/design_setup/hidpi/quality", "value", -1);
+    design->hidpi_thumbnail_quality = xml_file_get_node_attribute_long_with_default (xml, "/design_setup/hidpi/quality", "thumbnail", -1);
+  }
+
+
   /*  image_sizes section  */
   count = xml_file_node_get_children_count (xml, "/design_setup/image_sizes/size");
   for (i = 0; i < count; i++) {
@@ -268,6 +308,33 @@ parse_design_setup_xml (const gchar *filename)
     image_size->quality_threshold = xml_file_get_node_attribute_long_with_default (xml, s, "quality", DEFAULT_QUALITY_THRESHOLD);
     g_free (s);
 
+    /*  Generate HiDPI sizes  */
+    if (design->hidpi_sizes)
+      for (j = 0; design->hidpi_sizes[j] != 0; j++ ) {
+        hidpi_image_size = g_malloc0 (sizeof (TImageSize));
+        memcpy (hidpi_image_size, image_size, sizeof (TImageSize));
+        hidpi_image_size->is_hidpi = TRUE;
+        hidpi_image_size->hidpi_scale_factor = design->hidpi_sizes[j];
+        hidpi_image_size->hidpi_ref_size = image_size;
+        hidpi_image_size->tagname = NULL;
+        hidpi_image_size->fallback_size = NULL;
+        hidpi_image_size->quality_threshold = 0;
+        hidpi_image_size->no_resize_threshold = 0;
+        hidpi_image_size->availability_threshold = 0;
+        hidpi_image_size->name = g_strdup_printf (HIDPI_NAME_FORMAT, image_size->name, hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->landscape_width = lround ((gdouble) image_size->landscape_width * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->landscape_height = lround ((gdouble) image_size->landscape_height * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->portrait_width = lround ((gdouble) image_size->portrait_width * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->portrait_height = lround ((gdouble) image_size->portrait_height * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->square_size = lround ((gdouble) image_size->square_size * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->crop_width = lround ((gdouble) image_size->crop_width * hidpi_image_size->hidpi_scale_factor);
+        hidpi_image_size->crop_height = lround ((gdouble) image_size->crop_height * hidpi_image_size->hidpi_scale_factor);
+        if (! hidpi_image_size->is_thumbnail && design->hidpi_quality > 0)
+          hidpi_image_size->quality = design->hidpi_quality;
+        if (hidpi_image_size->is_thumbnail && design->hidpi_thumbnail_quality > 0)
+          hidpi_image_size->quality = design->hidpi_thumbnail_quality;
+        design->image_sizes = g_list_append (design->image_sizes, hidpi_image_size);
+      }
   }
   design->image_sizes = g_list_sort (design->image_sizes, (GCompareFunc) image_sizes_compare_func);
 
@@ -676,6 +743,7 @@ free_design_setup_data (TGalleryDesign *design)
     g_strfreev (design->supplemental_files);
     g_free (design->imgmagick_resize_opts);
     g_free (design->imgmagick_thumb_opts);
+    g_free (design->hidpi_sizes);
     g_free (design);
   }
 }