Google Picasa Collage File
Picasa is a program developed by Google that is used to organise and view digital images. There are versions available for Microsoft Windows and for Mac OS X as well as Linux.
Picasa Web Albums is similar in function to Flickr and allows users to share the digital pictures with others as albums.
Collage files which are a mixture of various images used to create one image in Picasa use the file extension .cxf.
» Google Picasa
How to open .cxf files?
Software to open .cxf files
What are .cxf files