Stretches image x horizontally by sr+1, and vertically by sc+1 while retaining the original image size and proportion.

def stretch_cv(x,sr,sc,interpolation=cv2.INTER_AREA):
    """ Stretches image x horizontally by sr+1, and vertically by sc+1 while retaining the original image size and proportion. """
    if sr==0 and sc==0: return x
    r,c,*_ = x.shape
    x = cv2.resize(x, None, fx=sr+1, fy=sc+1, interpolation=interpolation)
    nr,nc,*_ = x.shape
    cr = (nr-r)//2; cc = (nc-c)//2
    return x[cr:r+cr, cc:c+cc]