Preserve the file name as a sub-directory

This makes it easier to see where images originate from.

Author: Garanas

lib/jekyll/transcode-image-filters.rb

@@ -3,6 +3,15 @@
 
 module Jekyll
   module TranscodeImageFilters
+
+    # Computes a sanitized name for use as a directory.
+    # @param name The (file) name to sanitize.
+    # @return [String] 
+    def _sanitize_name(name)
+      # Replace invalid characters with `_` (Windows and Unix-safe)
+      name.gsub(/[<>:"\/\\|?*\n\r]/, '_').strip
+    end
+
     # Computes the name of the file in the cache.
     # @param absolute_path_source [String] Full path to the source file
     # @param resolution [String] As an example: 900x900
@@ -35,9 +44,11 @@ def _compute_paths(absolute_path_site, relative_path_source, cache_dir, resoluti
       absolute_path_source = File.join(absolute_path_site, relative_path_source)
       raise "No file found at #{absolute_path_source}" unless File.readable?(absolute_path_source)
 
+      file_name_source = _sanitize_name(File.basename(relative_path_source, ".*"))
+      file_name_source_sanitized = _sanitize_name(file_name_source)
       file_name_destination = _compute_cache_filename(absolute_path_source, resolution, format)
 
-      absolute_path_cache = File.join(absolute_path_site, cache_dir)
+      absolute_path_cache = File.join(absolute_path_site, cache_dir, file_name_source_sanitized)
       absolute_path_destination = File.join(absolute_path_cache, file_name_destination)
       relative_path_destination = File.join(cache_dir, file_name_destination)