Convert single unicode character to png image
Using ImageMagick:

convert -pointsize 64 -font /System/Library/Fonts/Apple\ Symbols.ttf label:⦿ output.png

convert -background transparent -fill 'hsb(0%,0%,0%)' -font /System/Library/Fonts/Apple\ Symbols.ttf -pointsize 64 -size 200x200 -gravity center label:⦿ output.png