C-Command Software Forum

Background images appearing the wrong size

Just to let other users know: I used GIMP to generate a background image in PNG format to use with DropDMG. The image was 640x480, but when imported into DropDMG it was scaled right down to roughly the same size as my 128x128 icons. When the .dmg was created, the image was the correct 640x480 size, but the folder was set to open in a much smaller size so only the top left corner of the image was visible.

After much faffing around, the answer is that GIMP by default saves the resolution (i.e. expected pixels-per-inch) in the PNG file. This seems to confuse DropDMG’s layout. If you save the PNG without the resolution info then DropDMG works fine.

An example image showing the problem is attached.

Thanks for the note. In my opinion, this is a bug in the Finder, which is not respecting the image’s dpi. At some point Mac OS X will support resolution independence, and then it would be desirable to ship a high-dpi background picture and not have it blown up.

If you want a screen-resolution background image, I suggest saving your PNG as 72dpi (or omitting the resolution info).