Add useful README

README.md

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-# python-rgbcx
-A python library for using the rgbcx texture compressor
+# Quicktex
+A python library for using DDS files
+
+Quicktex is a python library and command line tool for encoding and decoding DDS files.
+It is based on the [RGBCX encoder](https://github.com/drewcassidy/bc7enc), which is currently
+one of the [highest quality S3TC encoders available](https://aras-p.info/blog/2020/12/08/Texture-Compression-in-2020/).
+Quicktex has a python front end, but the encoding and decoding is all done in C++ for speed
+comparable to the original library.
+
+## Installation
+
+To install, first clone this repo and cd into it, then run:
+
+```shell
+pip install .
+```
+and setuptools will take care of any dependencies for you.
+
+If you are on macOS, it is recommended to install openMP from homebrew to enable 
+multithreading, since it is not included in the default Apple Clang install:
+
+```shell
+brew install libomp
+```
+
+The package also makes tests, stub generation, and docs available. To install the 
+required dependencies for them, install with options like so:
+
+```shell
+pip install .[tests,stubs,docs]
+```
+
+Quicktex will be available on Pypi once it is out of alpha.
+
+## Usage
+
+```
+Usage: quicktex [OPTIONS] COMMAND [ARGS]...
+
+  Encode and Decode various image formats
+
+Options:
+  --version  Show the version and exit.
+  --help     Show this message and exit.
+
+Commands:
+  decode  Decode DDS files to images.
+  encode  Decode DDS files to images of the given format.
+```
+
+To decode DDS files to images, use the `decode` subdommand, along with a glob or a
+list of files to decode. 
+
+To encode images to DDS files, use the `encode` subcommand, plus an additional
+subcommand for the format. For example, `quicktex encode bc1 bun.png` will encode
+bun.png in the current directory to a bc1/DXT1 dds file next to it.
+
+`encode` and `decode` both accept several common parameters:
+
+- `-f, --flip / -F, --no-flip`:  Vertically flip image before/after converting. 
+  [default: True]
+- `-r, --remove`: Remove input images after converting.
+- `-s, --suffix TEXT`: Suffix to append to output filename(s). 
+  Ignored if `output` is a single file.
+- `-o, --output`:  Output file or directory. If outputting to a file, input filenames 
+  must be only a single item. By default, files are converted in place.