How to resize .ico file with node-imagemagick

I try to resize the .ico file with node-imagemagick follow the code:

var im = require("imagemagick");

im.resize({
  srcData: fs.readFileSync('favicon.ico', 'binary'),
  width: 64
}, function(err, stdout) {
  // the stdout is null
})

the ico file buffer is null.

how to operate the ico file with node imagemagick, or is there any other node module to operate ico, png images?

ps: it is avaliable while the png file.