What can crypto verify here exactly? What stops me from: A. Writing my own software "camera" that does the same gyrations a real camera would do to sign its ra

What can crypto verify here exactly? What stops me from: A. Writing my own software "camera" that does the same gyrations a real camera would do to sign its raw image, but applied to an arbitrary unverified image file on my computer? or B. Printing out an unverified picture and taking a picture of that picture (with good lighting etc so that it is not obvious), with a camera that makes it verified "real"?