add unit/integrted tests for dpc

Yes, I will return it as well.

> On Dec 9, 2014, at 12:05 PM, Thomas A Caswell <notifications@github.com> wrote:
> 
> In skxray/dpc.py <https://github.com/Nikea/scikit-xray/pull/177#discussion-diff-21542994>:
> 
> > +
> > +        # Dimension reduction along x and y direction
> > +        imx, imy = image_reduction(im, roi, bad_pixels)
> > +
> > +        # 1-D IFFT
> > +        fx = np.fft.fftshift(np.fft.ifft(imx))
> > +        fy = np.fft.fftshift(np.fft.ifft(imy))
> > +
> > +        # Nonlinear fitting
> > +        _a, _gx = dpc_fit(ffx, ref_fx, fx, start_point, solver)
> > +        _a, _gy = dpc_fit(ffy, ref_fy, fy, start_point, solver)
> > +
> > +        # Store one-point intermediate results
> > +        gx[i, j] = _gx
> > +        gy[i, j] = _gy
> > +        a[i, j] = _a
> but it does not escape this function. If it is free and possibly interesting, why not return it along with phi?
> 
> —
> Reply to this email directly or view it on GitHub <https://github.com/Nikea/scikit-xray/pull/177/files#r21542994>.
> 

--
Best Regards,

  Cheng Chang 
  Computer Engineering, Stony Brook University
  Computer Science Group, Computational Science Center, Brookhaven National Laboratory
  Tel：(001) 631-885-4922