I have several Mac apps already created using another tool that I need to create Apple images for. They were created as PNG files without an alpha channel and stored in a folder.
I attempted to do the following command:
iconutil -c icons myfolder.iconset
I got multiple errors like below:
iconutil error: Unsuported image format
After reading this blog post along with a couple of posts on Stack Overflow I saw that I needed to have an alpha channel on my images. This is not stated in the Apple Developer documentation.
I tried using Preview for this but from the research I have done, including watching several videos I would have to remove a color which would mess up my icons, especially the smaller ones. My icons have a black background and attempting to remove what little white is on them would be a nightmare for the smaller icons.
There is a comment on this link by David Grayson that stated that ImageMagick could be used to add the alpha channel. The comment said that if I executed the following command for each png file that should work.
convert old_icon_16x16.png -define png:color-type=6 icon_16x16.png
However when I execute this I get the following error:
Abort trap: 6
I then went to this link referenced by the main ImageMagick website for examples. I tried the following command.
convert old_icon_16x16.png -alpha off -alpha on icon_16x16.png
I got the following error:
Abort trap: 6
I'm not sure where to go from here.