farbfeld

farbfeld is a lossless image format which is easy to parse, pipe and
compress.
It has the following format:

| Bytes | Description |
|--------|------------------------------------------------------------|
| 8 | "farbfeld" magic value |
| 4 | 32-Bit BE unsigned integer (width) |
| 4 | 32-Bit BE unsigned integer (height) |
| [2222] | 4⋅16-Bit BE unsigned integers [RGBA] / pixel, row-aligned |

http://tools.suckless.org/farbfeld/

>>2

Why 32 bit?

It's a power of 2, unlike 36. :P No, to be exact, there's no reason to go beyond that, given 2^36-1=4,294,967,295 is large
enough for anything. Even the largest images ever easily fit their sizes into 32 Bit. The next step would be 64, but that's overkill.

How am I supposed to make an efficient implementation in my PDP 10?

Sorry, no support for PDP-10's :P

Why RGBA? What if I want to use a better format?

A better format like? CMYK? Get off here man! :P
I actually worked on a CIELAB+Alpha implementation a year ago, it didn't work out though. I talked about it in my farbfeld talk at slcon2.

And why should I be limited to 64-bit-per-color?

*per-channel. Because you will probably not need more and I wanted to go for the 99.5%.

Now, I question, why does something that simple that even a kid could make depend on them?

The dependencies are needed to convert png's to the farbfeld format. It doesn't have anything to do with the format itself.
I went for libpng anyway because it's most widespread, even though it sucks balls.