Regarding the code at line 86-90 in liif.py

[ShuGuoJ]

"rel_cell = cell.clone()
rel_cell[:, :, 0] *= feat.shape[-2]
rel_cell[:, :, 1] *= feat.shape[-1]"

What does the code mean? Before that, rel_cell stores the proportion of 2 to crop_hr.shape. So, its multiplication resultant means what?

[shkarupa-alex]

As far as i understand:

cell = * 2 / [out_height, out_width]
rel_cell = cell * <input features height, width> = 2 * /

So rel_cell holds input-to-output scale for height and width as described in "Cell decoding" block of paper.

P.S.
I think cell decoding is useful for SR, but should be meaningless for most other tasks where input/output scale is constant.

[axhiao]

Hi guys, @shkarupa-alex @ShuGuoJ do you think the formula should be rel_cell[:, :, 0] *= feat.shape[-2]/2? Because the side length of each grid is 2/N

[ShuGuoJ]

Why is the side length of each grid 2/N? The N means what here.

[axhiao]

N means height or width of the feature map

[Zhaohuai-L]

Does it mean the decell is the 2/scale actually?