Add rounded macron-mask image

Done with:

convert img/macron-mask.png \( +clone  -alpha extract -draw 'fill black polygon 0,0 0,15 15,0 fill white circle 15,15 15,0' \( +clone -flip \) -compose Multiply -composite \( +clone -flop \) -compose Multiply -composite \) -alpha off -compose CopyOpacity -composite  img/macron-mask-round.png
2 jobs for macron-masque in 18 seconds
latest
Status Name Job ID Coverage
  Test
passed html-validity-check #719964

00:00:18

passed json-validity-check #719965

00:00:18