favicon.txt

# How to create a favicon with multiple image sizes and keep alpha transparency

- export your images in the desired sizes (16x16, 32x32 ... max 256x256) as PNGs + alpha
- install ImageMagick

Run this command (replacing the .png files for your own images):

    convert favicon-16.png favicon-32.png favicon-64.png -colors 256 -alpha background favicon.ico

The `-alpha background` options is what maintains the alpha channel. You can reduce colors even more if you want, be careful about file size - a favicon with all sizes up to 256px will hit > 100kb.

$ convert favicon-16.png favicon-32.png favicon-64.png \
    -bordercolor transparent -border 0 \
    -colors 256 -alpha background \
    favicon.ico

Add -bordercolor and -border option for anti-aliased result.

This great, although I do not understand

$ convert sapling.png  \
    \( -clone 0 -resize 16x16 \) \
    \( -clone 0 -resize 32x32 \) \
    \( -clone 0 -resize 48x48 \) \
    \( -clone 0 -resize 64x64 \) \
    -alpha background -colors 256 -delete 0 -bordercolor transparent -border 0 \
    favicon.ico

this great