Sure is edible as I work with birthday cakes at work and they often have pictures. If you're going to be doing this just for safetie's sake, do it with a new printer and only use it for cake printing.
A few years ago my canon printer came with a separate slip of paper saying please don't do this. There could not guarantee there wouldn't be ink or chemical in the printhead that are not intended for eating. I assumed it was more about liability then actual danger but it does show enough people were doing it do spook canon.
Presumably they print on rice paper and then stick it on? Or do you buy sheets of paper thin icing. Some canons used to have a thick slot at the back so you could stick a thick sheet of card straight though without bending which may have made them ideal.
I wonder if the light blue conservation fluid in a new Canon print head might be toxic. How much printing will be necessary to clean all of it out ? I don't like the idea of cake printing, wouldn't like to eat one of those cakes. And if the ink is edible, bacteria might thrive in it ?
Seeing this thread of edible ink made me curious so I did a little googling and found this :
I think you risk burning out both print head and logic board in the printer if just a little drop of water gets trapped behind the circuit board or the flexible flat cable. And that much water pressure from the cleaning tool can't be good for the gasket inside the print head or for the nozzles. I thought the LEDs on the cartridges were just ink level indicators, not that they could also indicate a clog. I wonder how the printer worked at all, when one cartridge seemed not to be seated properly ?
I have an older Canon that was for printing photos for cakes. The printer still works but the ink probably has all dried up. I stopped printing cakes because the forsting paper was expensive and the photo image was poor. It was fun for a while then it became boring. There were a few places where you order a cake and gave them a photo. They will make the cake with the photo printed on the icing on the cake. That's more than 10 years ago. I am surprised that it still exists today.