VL_NNCROP - CNN crop.
Y = VL_NNCROP(X, CROP) crops the input X spatially. CROP specifies the amount of cropping as [TOP, BOTTOM, LEFT, RIGHT].
DZDX = VL_NNCROP(X, CROP, DZDY) computes the derivative DZDX of the function projected on the output derivative DZDY. DZDX has the same dimension as X and DZDY the same dimension as Y.
DZDX = VL_NNCROP(, CROP, DZDY, INPUTSIZE) is an alternative to the previous call in which X is omitted and its size is passed as INPUTSIZE.