Chrome Extension のアイコン複数サイズ作るの面倒くさい ref: http://qiita.com/ygkn/items/efa1e311006f5c900123

generate_icons.sh

#!/bin/bash

for size in 16 48 128
do
  convert icons/source.png -resize ${size}x  -unsharp 1.5x1+0.7+0.02 icons/${size}.png
done

manifest.json_(iconのみ抜粋)

{
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  }
}