How to transform SoundWave Picture to sound?
I don't think "I love you" is doable with a sound wave image, because that's already very roughly about 200 cycles of the fundamental frequency of the voice, and you need also the harmonics so that it sounds right and can be understood. Too much horizontal resolution is needed to pack that into a tattoo.

You could probably pull it off as a spectrogram.

I've seen ads for a commercial service that presumably stores at a server a database of sound clips each associated with a sound wave image. Then their phone app sends the tattoo photo to the server and plays back the sound clip associated with the image that most resembles the tattoo photo. Technically that's not far different from having the sound clip number tattooed as a bar code.