author = 'aresowj'

''' Analyse a file and see if it is a BMP. Print the size and color depths if true. '''

import re, struct

def isBMP(header): '''Using the header data to judge if the file is a BMP.'''

result = struct.unpack('<ccIIIIIIHH', header)
if not result[0] == b'B' and result[1] == b'M':
    print('\nThe file is not a BMP.')
else:
    print('\nThe file is a BMP.')
    print('The size of this file is ' + str(result[6]) + 'x' + str(result[7]) + '.')
    print('The color depth of this file is ' + str(result[9]) + 'bits.')

def isValidFilename(fn): fnre = re.compile(r'^([a-zA-Z0-9!\@#\$\%\^\&()-\+\=]+).([a-zA-Z0-9!\@#\$\%\^\&()-_+\=]+)') #Use regex to judge if it is a valid filename. fn_match = fn_re.match(fn) if fn_match:

    #print(fn_match.groups())    #Showing all the matched groups
    return True

return False

def main(): '''Open a file and read the first 30 bytes as the header.''' fn = '' header = b'' while True: fn = input('\n\nPlease input the file name.\nThe file should be in the same folder of this Py script: ') if not isValidFilename(fn): continue

    with open(fn, 'rb') as f:
        header = f.read(30)
        print(header)

    isBMP(header)

if name == 'main': main()