“Combine High Resolution Artwork” in XCode 4?

Question

In XCode 4 when working on an iOS project (maybe it was in XCode 3 too and I just hadn't noticed it) there is field under build settings called "Combine High Resolution Artwork", which can be set to yes or no.

What exactly does this setting do?

Answer 1

From Xcode's quick help:

Combine High Resolution Artwork COMBINE_HIDPI_IMAGES

Combines image files at different resolutions into one multi-page TIFF file that is HiDPI compliant for Mac OS X 10.7 and later. Only image files in the same directory and with the same base name and extension are combined. The file names must conform to the naming convention used in HiDPI. [COMBINE_HIDPI_IMAGES]

In other words, the setting probably has no effect under iOS at the moment. It would combine abc.png and [e-mail] into one multi-page TIFF file, which would be convenient under OS X because NSImage can handle such files and use the image representation that is best suited for the desired output size and device. If future Apple hardware will have higher screen resolutions, this setting will probably play an important role in how developers deal with it.