Extensis, a wholly owned subsidiary of ImageX since 2000, employs 66 staff at its UK office in Northampton and its headquarters in Portland, Oregon.
The companys UK operation is headed up by business manager Richard Bamford. Extensis general manager Craig Keudell will step up to become group chief executive.
Celartem will pay another 1.3m over the next two years if Extensis meets revenue targets.
Celartem was set up in 1996 to conduct research and development into storage and distribution for digital images.
It was listed on the NASDAQ Japan market in December 2001.
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