I am trying to set an image as the background in the window of a DMG. The image is: PNG file; 144x144 resolution; 1138x574 size.
In macOS Tahoe, the image is added by: selecting the DMG window; opening the "Show View Options" dialog; clicking on "Picture"; dragging the image file to the small square box labelled "Drag image here"; closing "Show View Options" dialog. The DMG is then ejected. In Disk Utility, the image file is converted to "Read Only image (UDRO)".
The converted image file is opened and the background image is visible. The image file is then copied to a MacBook running macOS 12 Monterey and opened. The background image is NOT shown. The image file is copied to a Mac mini running macOS 14 Sequoia and opened. The background image is NOT shown.
Have read past online discussions in which it was explained that an image file called "background" should be inside a hidden folder called ".background". The above procedure did not do that. Is that old advice still correct for macOS Tahoe ?
Has Tahoe somehow broken the method used for setting the background of a Window ?
Is the method used in Tahoe different to past versions of macOS ? If so, is there a way of maintaining compatibility with old versions of macOS ?
Is there any documentation on how to set the background image of a DMG window which might explain this behaviour ??
Thanks.