The keyword you're looking for is "Steganography". See, for example, https://stackoverflow.com/questions/20863721/image-steganography-that-could-survive-jpeg-co

The keyword you're looking for is "Steganography". See, for example, https://stackoverflow.com/questions/20863721/image-steganography-that-could-survive-jpeg-compression https://stackoverflow.com/questions/20863721/image-steganogr....