It can be done with LSB based image steganography I think.
Let's try :)

why not use the tEXt PNG chunk ? Althought it says it should not contains null characters, since it isn't meant for display this shouldn't matter much as the text string is not null-terminated.

However with this method, data will be lost if converting from PNG to any other image format.
But it has the added benefit of being way easier to implement.

why not use the tEXt PNG chunk ?

Some sites will strip this data as it's not relevant for display.

I did some experiments with embedding a cart to png image on png-test branch.

Original 256x256 image (9 877 bytes):

With embedded BALMUNG cart (80 663 bytes):

Very pleased with the result, almost no difference is visible.
Also, we have to design a 256x256 cartridge template with a cover and game info now...

Looks like an opportunity for a design contest. Having a simple, recognizable, and striking design could be an important part of TIC-80's visibility.

Welcome if you have ideas :)

Is there any specific requirements like size of the image, dimensions, some ares dedicated for user to draw on like redshift disks have?

I think 256x256 with 240x136 cover inside is the main requirement.

How the cartridge could look (WIP)

Could we put the cartridge "size" on the outside maybe? Some calculation of # of banks used + code size, etc...

i like this idea very much! the wip cartridge has already a nice look.

some thoughts & questions:

• text "TIC-80" should be present somewhere
• maybe the TIC-80 mascot, too!
• pins at bottom instead of top?
• it would be nice to be able to decide the color of the cartridge, famicom style
• could one fit pro cartridges in 256*256 images as well?

Some progress:

Thank you for the thoughts :)
Pro carts fit 256x256 without any problems.

Looks great! Personally, I like the dark one (the first) the most. Keeping with the Sweetie-16 color palette and feel is important.

Me too :)

This is the tiny font we are using in TIC80. I'm always trying to use the default font and default sweetie16 palette colors to design such things.

Even if the end result is worse [in that overall legibility suffers]? Did you try a variant with "cartridge" in caps?

You are keeping in mind not everyone is going to ZOOM these cartridges to read what it written on them...? If the text is illegible when the image is shown at a small size then it's really just decoration... For example as embedded here on Github I find it quite hard to read the text even if I'm squinting (font plus tiny size plus low contrast)...

I've always placed a high value on usability/accessibility.

I'd go with the smaller font even for the game title & game creator names!

You wouldn't need to have that long titles to overflow with the current design. Besides, if the game creator wants, they can feature the game title (and their name) more prominently in the cover image.

That would be more in line with actual game cartridges (and comparable to game banner images in online marketplaces), for that matter.

Besides, if the game creator wants, they can feature the game title (and their name) more prominently in the cover image.

I did have this thought earlier as well... most video game cartridges have a single sticker and that serves multiple purposes for logo/branding/name/etc... I think really what would be cool here is if the cartridge was really more of a "physical good"... and if someone wanted to make a special cartridge they could design it however they wanted. Make it blue. Have a larger graphic. Add decorative molding... just so long as it still had the correct "shape" and "pinout". :-) [of course those things are largely irrelevant also technically speaking]

I plan on doing RetroJam in the next week or so so if I have time I might see if our artist would want to try their hand at making a custom spiffy cartridge PNG. :-)

@nesbox Do you have any issue with people doing custom carts on their own - ie if the community makes some tools to make that super easy to do would you fight that by making the official binary start inspecting the images for the official template or something along those lines? Or just os long as the binary data was encoded properly it would work, period?

Do you have any issue...

I'd like we have one common cart template with TIC logo and URL and allow the user to design the "sticker" he wants, with labels and other things.
The current design could be provided by default but technically, it doesn't matter for TIC how the cart looks, it just tries to decode the image, and the user allowed to encode the cart to any 256x256 png he wants.

I'd like we have one common cart template with TIC logo and URL and allow the user to design the "sticker" he wants, with labels and other things.

I generally have no problem with the logo and URL, only the font - I'm talking more bigger picture design elements, plastic color, molding, etc. Not sure if we're talking past one another or not. I definitely see the need/desire for a "brand" of cartridge that everyone gets by default - for use as a marketing tool. I don't think everyone will do their own, it would just be nice if it was a thing that remains doable. :-)

And generally if they did it "tastefully" I'd hope it would still look like a "special edition" TIC-80 cartridge, not "something else". Gameboy cartridges are still quite recognizable regardless of plastic molding color, because they have a distinctive size and shape, etc... and speaking of Gameboy...

For example right now I'm looking at doing a Gameboy Color game for RetroJam (letterboxed on TIC-80)... and if all you do is decode the data then I could make a 256x256 that looked more like an actual Gameboy cartridge - in keeping with the Jam theme - but still could just drag and drop if all you cared about what the raw data. :)

That's more of an exception case though, but still neat if possible.

but technically, it doesn't matter for TIC how the cart looks, it just tries to decode the image

Very good news.

Added PNG cart saving/loading here 335d795
Use save name.png command to check.

Example cart, just drag it to tic80.exe:

These should be available to download from the tic.computer website along with the standard cart

@ChildishGiant sure, will be added

What is the maximum cartridge size for saving to png?