chromium/third_party/blink/web_tests/css3/filters/effect-grayscale.html

<img style="filter: grayscale(0)" src="resources/reference.png">
<img style="filter: grayscale(0.2)" src="resources/reference.png">
<img style="filter: grayscale(0.4)" src="resources/reference.png">
<img style="filter: grayscale(0.6)" src="resources/reference.png">
<img style="filter: grayscale(0.8)" src="resources/reference.png">
<img style="filter: grayscale(1.0)" src="resources/reference.png">