How do I use ThemeEngine?

[YousufSSyed]

How do I replace the images in a .car file with news ones? I have no idea after looking at the UI. the buttons "Add Element" and "Add Rendition" don't do anything. btw, I'm on an Intel Mac with Big Sur 11.5.2.

[borp99]

Once you've opened your xxx.car file, select the icon category from the left side list and 2 or more images belonging to that group will show up on the main RHS pane window. You can drag each of these icons onto your desktop to edit them or, if using different icons, just drag these replacements (usually PNG or TIFF images) over the top of the appropriate one in the RHS pane. ThemeEngine always converts them to PNG regardless. Note that when you click on one of the original icons, its size eg. 256x256, 16x16, 512x512 and some with '@2x' versions [if the final car file may be used on a Mac 'retina' display or some other double resolution monitor] will be displayed in the top right hand corner. Make sure you copy back or replace 'like for like' sizes. Once you've finished, save the car file or, probably better, 'save as' to a new car file, ready to replace it where necessary in the system, library or user library folder.

If you have one new design you want to inject into a car file, find a suitable app, like Image2Icon - available for free from the AppStore (the paid advanced features aren’t required). Export to ‘Iconset’ and you'll end up with a full set of icons at all of the standard Apple sizes to use with ThemeEngine. I also use Icon Maker Pro, which can create the newer shaped 'square with round corners' icons used for Big Sur and Monterey.