Addy Osmani on Twitter: "Great guide to CSS mask-image: https://t.co/fWLWAGdVvM ~ specify an image or gradient to use as a mask layer. By @rachelandrew https://t.co/QOptFxOHSa" / Twitter
CSS & SVG Masks (Test cases)
CSS Masking - Ahmad Shadeed
mask-mode | CSS-Tricks - CSS-Tricks
CSS Mask and Clip-path property Effect on Images | Quick Guide