libptouch の更新に追従

ruby/lib/libptouch/context.rb

@@ -87,7 +87,7 @@ module Libptouch
       raw = out_pp.read_pointer
       raise Libptouch::Error.new(OK, "null raster from PNG") if raw.null?
 
-      len = out_len.read_size_t
+      len = out_len.get(:size_t, 0)
       bytes = raw.read_bytes(len)
       Binding.libptouch_free_raster(raw)
       [bytes, out_params[:width_dots], out_params[:height_dots]]