You will need to do your own investigation on RGB<->HSL conversion and writing/using shaders. It's difficult that somebody will write and post a ready-to-use program for you. You can discuss the very same topic on the many different forums, but until you start working on it yourself - it won't help.

Indeed, learning shaders will be a time consuming experience, so you have several options:

1) Learn shaders, write your own to solve the problem. (pros: a lot of fresh knowledge; cons: time consuming)

2) Use some kind of software rendering to solve your problem. (pros: slow, can't be used in real-time; cons: less time required)

3) Hire someone to solve the problem for you (pros: quickly resolve the problem; cons: it might be expensive)

4) Change the problem so you don't need to use per-pixel HSL-RGB transformations in real-time. (pros: no need to invest time and money; cons: may not be possible depending on your requirements)

Yes, shaders will work for you, and no, they are not "completely canned algorithms", and yes, you can set arbitrary values at runtime.