在python中如何将图像从(n,m,4)重塑为(n,m,3)?

A = [[[  7,  23,   0, 255],
         [ 14,  25,   1, 255],
         [ 23,  26,   1, 255],
         [ 49,  41,  33, 255],
         [ 43,  37,  30, 255],
         [ 42,  33,  25, 255]],

        [[ 59,  69,  59, 255],
         [ 77,  83,  72, 255],
         [ 86,  91,  84, 255],
         [ 16,  16,   8, 255],
         [  9,   7,   2, 255],
         [  1,   0,   0, 255]]]

print(np.array(A).shape) ## (3,6,4)

我想把它改造成这样 (3,6,3) 以至于我想跳过 255

我该怎么办?