calculate_inverse_fft: _BoundsI ymax value?

[jecampagne]

Hi looking at image.calculate_inverse_fft I was wandering why target_bounds ymax value is No2-1 and not No2, I guess it is a to fit FFT requirements. In fact this is also the case in drawFFT_finish by the way. Thanks

[rmjarvis]

Because the sizes have to be even. Well, they don't have to be, but it's way faster if the size is a power of 2 or 3 x a power of two, so we enforce that for all our FFTs.