Looking into this a bit more, it does look as if Xcode isn't going to let you do this in one drag and drop move. That said, I don't think it'd be that hard to create a script to do this.
Contrary to what I said earlier, I realise it would be trivial to adapt the Automator workflow from my website, as we don't actually need or want the iconutil command anymore since we don't want to make an icns file at all. Most of the size re-scalings are already in there (for Mac OS X), you can just add/delete the ones you need/don't want, following the same pattern of actions (you need to open the app in Automator and you'll see its fairly obvious how it works).
Also, the .json file in Image.xcassets/AppIcon.iconset/contents.json can be edited manually in TextWrangler. It has the form
{
"images" : [
{
"idiom" : "iphone",
"size" : "29x29",
"scale" : "2x"
},
{
"idiom" : "iphone",
"size" : "40x40",
"scale" : "2x"
},
{
"idiom" : "iphone",
"size" : "60x60",
"scale" : "2x"
},
....
and so on for all the other sizes, until
.... ],
"info" : {
"version" : 1,
"author" : "xcode"
}
}
When you add a file from the project sidebar by dragging and dropping what it actually does is add the 'filename' key, so you get something of the form
"size" : "256x256",
"idiom" : "iphone",
"filename" : "myIcon256.png",
"scale" : "1x"
for each one, where the pink bits are obviously variables that change for each format.
So, the general form of a solution would be to have a couple of scripts, one (could be done in Automator or AppleScript) that takes a single 1024x1024.png and creates all the requisite sizes, and another that takes the name of the png, and outputs a plain text file called Contents.json that has the structure above, adding the filename and number to each block. That's probably a job best done with a bash script. All you do then is drag the multiple images to the project sidebar, and drag the new 'contents.json' file into the xcassets/AppIcon.iconset folder.
Well, that's the basic form of a solution, and I suppose once having got that far you could wrap it all up into an neat little xcode utility package and sell it on the app store! 🙂
I guess I'll think about writing a free utility to do this at some point, but I don't know how long it'll take me to get round to it. Maybe someone else can take this idea and run with it? If not, I'll put it on my to-do list, but right now that's already pretty long so don't hold your breathe. If I ever do get round to it, I'll post a link back here.
