Qt Creator编译mac程序时，需要icns作为应用程序图标。

    1. mkdir MyIcon.iconset
    2. sips -z 16 16     Icon1024.png --out MyIcon.iconset/icon_16x16.png
    3. sips -z 32 32     Icon1024.png --out MyIcon.iconset/icon_16x16@2x.png
    4. sips -z 32 32     Icon1024.png --out MyIcon.iconset/icon_32x32.png
    5. sips -z 64 64     Icon1024.png --out MyIcon.iconset/icon_32x32@2x.png
    6. sips -z 128 128   Icon1024.png --out MyIcon.iconset/icon_128x128.png
    7. sips -z 256 256   Icon1024.png --out MyIcon.iconset/icon_128x128@2x.png
    8. sips -z 256 256   Icon1024.png --out MyIcon.iconset/icon_256x256.png
    9. sips -z 512 512   Icon1024.png --out MyIcon.iconset/icon_256x256@2x.png
    10. sips -z 512 512   Icon1024.png --out MyIcon.iconset/icon_512x512.png
    11. cp Icon1024.png MyIcon.iconset/icon_512x512@2x.png
    12. iconutil -c icns MyIcon.iconset
    13. rm -R MyIcon.iconset

    来源：https://stackoverflow.com/questions/12306223/how-to-manually-create-icns-files-using-iconutil