First, a fair warning. Although this article describes a rather simple and easy-to-use application, you need a working knowledge of Linux and PHP to understand what it's about.
Being a lazy amateur photographer, I prefer to keep my editing workflow to a minimum. So in most cases I'm happy doing basic adjustments and then applying a preset from my small collection of hand-made curves.
This approach works well when I'm editing photos in digiKam on my main machine. But if I want to use my curve presets to quickly process photos on my Android device or on my iPad, I'm out of luck. To solve the problem, I've built Lilut, a simple web application that I can use to upload a photo, apply one of the available presets to it, and download the result -- all done in one smooth action. And since Lilut uses Hald CLUT files, the presets can include not only curve adjustments but also color tweaks. If you are not familiar with what Hald CLUT is, the Film Simulation article in Rawpedia provides a good primer on the topic.
Creating your own Hald CLUT files from scratch or using existing curve and color adjustments is relatively straightforward. I use digiKam for that, but you can use practically any photo editing application. And Lilut comes with a base file you can use as a starting point for creating Hald CLUT files. And you can also grab my own Hald CLUT Pack.
Although Lilut is by design a supremely simple tool, it does have a couple of tiny creature comforts. By default, Lilut doesn't store any files, but you can configure it to save the uploaded and processed images. And if you don't fancy the default dark look, you switch to a different theme by specifying it in the config.php file.
Lilut is written in PHP, and it will happily run on a Linux machine with a web server and PHP. The only additional requirement is the php-imagick library (the Linux Photography book provides detailed instructions on how to install Lilut). For my own Lilut installation, I bought a cheap VPS from Contabo for a paltry €4 a month (no affiliation, just a satisfied customer) and registered a domain name with Namecheap for the princely sum of \$1.18. Don't want to bother with VPS? No problem: throw Lilut on a Raspberry Pi, and you are good to go.
If you want to try Lilut out, head over to Lilut's website. Lilut doesn't keep uploaded and processed files.