When you eat animals you give the market a financial incentive to breed and slaughter more animals, who inevitably have to eat a bunch of plants to grow. It’s not that you eating a burger kills a cow, but you eating a burger helps make it financially sound and socially acceptable to murder cows for burgers.
PNG is fine for this. A palletized PNG on max compression would be smaller than the game and totally lossless unlike this. First you gotta take this image and map/quantize it to the original palette though to destroy the JPEG artifacts, which produce colors in between ones that would have existed in the game’s output.