Here are some places where you can look for information about imcalc: Batch image calulations and transformations (SPM5/8/12):

Homepage
imcalc: Batch image calulations and transformations (SPM5/8/12) has a homepage that can be found at http://tools.robjellis.net/
Wiki
imcalc: Batch image calulations and transformations (SPM5/8/12) has a wiki that can be found here.