Favicon.ico from transparent png

convert ~/Scrivania/favicon.png \
    \( -clone 0 -resize 16x16 \) \
    \( -clone 0 -resize 32x32 \) \
    \( -clone 0 -resize 48x48 \) \
    \( -clone 0 -resize 64x64 \) \
    -delete 0 -alpha on -background transparent ~/Scrivania/favicon.ico