How to remove DC offset from matrix dataset?

I want to remove DC offset from the dataset in M1.mat(available in attachment). The dataset is 128*256 & complex valued. How to remove DC offset using MATLAB?

[dpb]

Not sure what it means to detrend a complex variable, precisely,

detrend thinks it means to subtract mean of real and imaginary components; but that can change phase drastically so may or may not make any sense depending upon what is next step(s).