Show HN: Small C Program to Convert Photos to Audio

If it's just through a cheap speaker and mic, you'll probably lose a lot of the image.

This uses a linear frequency scale (which is just the nature of Fourier transforms), whereas our ears are sensitive on a log frequency scale. In other words, the information that's most important to our hearing, which is what a mic & speaker will preserve the best, is in the bottom 10% of the image.

A cheap speaker & mic will probably lose a lot of content above about 10 kHz - which is the entire top half of the image. Even though this wouldn't be that huge a difference to our ears, it would sure look bad in the image.

As for background noise, the difference would probably look like the difference here: http://www.sweetwater.com/insync/media/2010/09/RXAdv-e-xlarg... (that's a screenshot of audio restoration software that removes noise, so it's technically doing the opposite process as best it can, but the difference would be similar).

This isn't exactly related (as it doesn't produce a spectrogram), but the software pixivisor plays around with this idea: http://warmplace.ru/soft/pixivisor/

The software can act as a transmitter or receiver. In trasmitter mode, you can provide it a static image or animated gif, which it will convert into audio which plays continuously. In receiver mode, pixivisor listens via the mic or line-in (depending on hardware platform and whats attached) and reconstructs the image from the audio. You can then manipulate the audio however you want.

This demo uses a korg monotron's low pass filter and LFOs to mangle an animated gif of a cat: https://www.youtube.com/watch?t=63&v=g2W1W4fwEkg

Its really interesting to me to see how the audio modulation is represented in the receiver's output.

+1 stb_image.h it uses a good interface for an image loading library, something nobody seems capable of even in the "good ol' days"... just a shame it doesn't support more of PNG (16-bit channels would be nice, and support for bigger images too)

using libpng, libjpeg etc. however is a massive pain with lots of work required even if you just want to do what everyone does pretty much and load a file into RGBA buffer and get back the width and height. :)

transfer it via phone line, you'll got facsimile