numpy中，从一片c_void_p指向的区域里获取数据

以前采用的数据拷贝的笨办法：

1 bitmap_size = (1080, 1920, 3)
2 buf = create_string_buffer(bitmap_size[0]*bitmap_size[1]*bitmap_size[2])
3 pointer_data = c_void_p(addressof(xxxx))
4 memmove(buf, pointer_data, bitmap_size[0]*bitmap_size[1]*bitmap_size[2])
5 #
6 np_arr = np.frombuffer(buf, dtype=np.uint8, count=bitmap_size[0]*bitmap_size[1]*bitmap_size[2])
7 np_arr = np_arr.reshape(bitmap_size)

现在找到了更好的办法，不用拷贝数据：

1 bitmap_size = (1080, 1920, 3)
2 bytes_count = bitmap_size[0]*bitmap_size[1]*bitmap_size[2]
3 pointer_data = c_void_p(addressof(xxxx))
4 #定义一个指向数组的指针
5 array_pointer = cast(pointer_data, POINTER(c_char*bytes_count)))
6 np_arr = np.frombuffer(array_pointer.contents, dtype=np.uint8, count=bytes_count)
7 np_arr = np_arr.reshape(bitmap_size)