import struct

pic='qq.bmp'
def ifbmp(pic):
    f=open(pic,'rb')
    f1=f.read(30)
    p=struct.unpack('<ccIIIIIIHH',f1)
    if isinstance(p[0],bytes) and isinstance(p[1],bytes):
        print('该图片是位图文件！',end='')
        formaT='%s * %s' %(p[6],p[7])
        color=p[-1]
        print('它的位图大小为%s,颜色数为%s' %(formaT,color))
    else:
        print('该图片不是位图文件！')