Final answer:
To send a card with a hidden text message and decode it, you can use Python and additional libraries such as 'smtplib' and 'PIL'.
Step-by-step explanation:
To send a card with a hidden text message and decode the hidden message, you can use the Python programming language and some additional libraries. First, you will need to use the 'smtplib' library to send the email with the card image as an attachment. You can then use the 'PIL' library to manipulate the image and hide the text message within it. To decode the hidden message in the received card, you can reverse the process by extracting the hidden information from the image using the 'PIL' library.