thumb: strip metadata and chroma

Decreased colour quality recommended by Google PageSpeed:
<https://developers.google.com/speed/docs/insights/OptimizeImages>

diff --git a/thumb/index.php b/thumb/index.php
index c65cab3dab9ea7ebb2227ded9e4a2b984b845d7e..d296fbf1560e0f4d339912fa7e9aa6f8c5f575b9 100644 (file)
--- a/thumb/index.php
+++ b/thumb/index.php
@@ -91,6 +91,8 @@ function mkthumb_exec($source, $target, $width, $height)
                '-trim',
                '-background', 'white', '-layers', 'flatten', # opaque
                '-interlace', 'plane', # progressive
+               '-strip', '-taint', # omit metadata
+               '-sampling-factor', '4:2:0', '-colorspace', 'sRGB', # half chroma
                '-resize', "${width}x${height}",
                '-quality', '85%',
                $source, "jpg:$target"