optimizeimages: add oxipng support

docs/config.rst

@@ -777,6 +777,24 @@ Image options
 
             **Default:** ``2``
 
+    ``oxipng``
+        An optipng replacement written in Rust. Works much like optipng.
+        ``olevel``
+            An integer between ``0`` (few optimizations) and ``6`` (many
+            optimizations). The default should be satisfactory for everyone,
+            higher levels than the default see almost no benefit.
+
+            **Default:** ``2``
+
+        ``threads``
+            An integer specifying how many threads per process to use. Note that
+            Overviewer spawns one oxipng process per Overviewer worker process,
+            so increasing this value if you already have one Overviewer process
+            per CPU thread makes little sense, and can actually slow down the
+            rendering.
+
+            **Default:** ``1``
+
     ``pngcrush``
         pngcrush, like optipng, is a lossless PNG recompressor. If you are able to do so, it
         is recommended to use optipng instead, as it generally yields better results in less

overviewer_core/optimizeimages.py

@@ -192,6 +192,26 @@ class jpegoptim(Optimizer, JPEGOptimizer):
             return True
 
 
+class oxipng(Optimizer, PNGOptimizer):
+    binarynames = ["oxipng"]
+
+    def __init__(self, olevel=2, threads=1):
+        if olevel > 6:
+            raise Exception("olevel should be between 0 and 6 inclusive")
+        if threads < 1:
+            raise Exception("threads needs to be at least 1")
+        self.olevel = olevel
+        self.threads = threads
+
+    def optimize(self, img):
+        Optimizer.fire_and_forget(self, [self.binaryname, "-o" +
+                                         str(self.olevel), "-q", "-t" +
+                                         str(self.threads), img])
+
+    def is_crusher(self):
+        return True
+
+
 def optimize_image(imgpath, imgformat, optimizers):
         for opt in optimizers:
             if imgformat == 'png':