How to manually create icns files using iconutil?

Checkout the following instructions (link):

Use iconutil to Create an icns File Manually

The iconutil command-line tool converts iconset folders to deployment-ready, high-resolution icns files. (You can find complete documentation for this tool by entering man iconutil in Terminal.) Using this tool also compresses the resulting icns file, so there is no need for you to perform additional compression.

To convert a set of icons to an icns file

Enter this command into the Terminal window:

iconutil -c icns <iconset filename>

where <iconset filename> is the path to the folder containing the set of icons you want to convert to icns. The output is written to the same location as the iconset file, unless you specify an output file as shown:

iconutil -c icns -o <icon filename> <iconset filename>

In other words, you need to replace <iconset filename> by the path:

/Users/myname/SDK Mac Apps/MyApp/grafica/icon.iconset

Since the path contains spaces, you need to use double quotes, for example:

iconutil -c icns "/Users/myname/SDK Mac Apps/MyApp/grafica/icon.iconset"

This command should work properly.

Here's a script to convert a 1024x1024 png (named "Icon1024.png") to the required icns file. Save it to a file called "CreateICNS.src" in the folder where your png file is then in terminal "cd" to the same folder and type "source CreateICNS.src" to call it:

mkdir MyIcon.iconset
sips -z 16 16     Icon1024.png --out MyIcon.iconset/icon_16x16.png
sips -z 32 32     Icon1024.png --out MyIcon.iconset/[email protected]
sips -z 32 32     Icon1024.png --out MyIcon.iconset/icon_32x32.png
sips -z 64 64     Icon1024.png --out MyIcon.iconset/[email protected]
sips -z 128 128   Icon1024.png --out MyIcon.iconset/icon_128x128.png
sips -z 256 256   Icon1024.png --out MyIcon.iconset/[email protected]
sips -z 256 256   Icon1024.png --out MyIcon.iconset/icon_256x256.png
sips -z 512 512   Icon1024.png --out MyIcon.iconset/[email protected]
sips -z 512 512   Icon1024.png --out MyIcon.iconset/icon_512x512.png
cp Icon1024.png MyIcon.iconset/[email protected]
iconutil -c icns MyIcon.iconset
rm -R MyIcon.iconset