Objectivo
Desarrollar un programa Python para cifrar o descifrar un archivo de imagen BMP intercambiando la firma "BM" en los dos primeros bytes por "MB" y viceversa.
Utilizar el constructor avanzado FileStream para permitir la lectura y la escritura al mismo tiempo.
Ejemplo Ejercicio Python
Mostrar Código Python
# Python program to encrypt or decrypt a BMP file by swapping the "BM" signature
def encrypt_decrypt_bmp(filename):
try:
# Open the BMP file in binary read and write mode
with open(filename, 'r+b') as file:
# Read the first two bytes (the signature)
signature = file.read(2)
# Check if the signature is "BM"
if signature == b'BM':
print("Encrypting: Swapping 'BM' to 'MB'...")
# Move the file pointer back to the start
file.seek(0)
# Write "MB" to replace "BM"
file.write(b'MB')
elif signature == b'MB':
print("Decrypting: Swapping 'MB' to 'BM'...")
# Move the file pointer back to the start
file.seek(0)
# Write "BM" to replace "MB"
file.write(b'BM')
else:
print(f"Error: The file '{filename}' does not have a valid BMP signature.")
except FileNotFoundError:
print(f"Error: The file '{filename}' does not exist.")
except Exception as e:
print(f"Error: {str(e)}")
# Example usage
encrypt_decrypt_bmp("example.bmp")
Output
Encrypting: Swapping 'BM' to 'MB'...
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