--- /dev/null
+# Nick's web site: imgresize filter. Helper for resizing images during site
+# compilations for thumbnails, etc.
+#
+# Copyright © 2016, 2020 Nick Bowler
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+class ImgResize < Nanoc::Filter
+ identifier :imgresize
+ type :binary
+
+ def run(filename, params = {})
+ w = if params[:width] then params[:width].to_i end
+ h = if params[:height] then params[:height].to_i end
+ scale = [w, h && "x", h].join
+
+ args = ["-scale", scale, filename]
+ case filename
+ when /\.jpg$/
+ args << "-quality" << "85"
+ end
+ args << output_filename
+
+ system('gm', 'convert', *args)
+ end
+end