Update README.md

Author: nleseul

README.md

@@ -1 +1,86 @@
 # obs-ghostscript
+
+## Introduction
+
+The obs-ghostscript plugin is intended to allow an easy way to include a specific PDF document (or other type 
+supported by the [Ghostscript](https://ghostscript.com/) library) in your [OBS Studio](https://obsproject.com/) 
+scenes. It should be a simpler alternative to using a window capture source to show the contents of an Acrobat 
+window.
+
+The document is shown one page at a time, and the current page can be updated real-time through an interaction
+window to scroll through a document live during a capture session. 
+
+## Installation
+
+The binary package mirrors the structure of the OBS Studio installation directory, so you should be able to
+just drop its contents alongside an OBS Studio install (usually at C:\Program Files (x86)\obs-studio\). The 
+necessary files should look like this: 
+
+    obs-studio
+    |---data
+    |   |---obs-plugins
+    |       |---obs-ghostscript
+    |           |---locale
+    |               |---en-US.ini
+    |---obs-plugins
+        |---32bit
+        |   |---gsdll32.dll
+        |   |---obs-ghostscript.dll
+        |---64bit
+            |---gsdll64.dll
+            |---obs-ghostscript.dlll
+
+## Usage
+
+The source is called "PDF Document (Ghostscript)" in OBS Studio's source creation menu. The properties to set
+on it are the path to the document file and the page from the document which should be shown. 
+
+By right-clicking on the source and choosing "Interact", you can manipulate the current page more quickly while
+recording/streaming than the source properties dialog allows. With the source displayed in an interaction window,
+you can scroll your mouse wheel and change the displayed page. (Note that the source will only receive mouse 
+events if the mouse is hovered over the image shown in the intraction window.)
+
+## Building
+
+If you wish to build the obs-ghostscript plugin from source, you should just need [CMake](https://cmake.org/), 
+the OBS Studio libraries and headers, and the Ghostscript libraries and headers. 
+
+* [obs-ghostscript source repository](https://github.com/nleseul/obs-ghostscript)
+* [OBS studio source repository](https://github.com/jp9000/obs-studio)
+* [Ghostscript source repository](http://git.ghostscript.com/?p=ghostpdl.git;a=summary)
+
+I don't believe that the OBS project provides prebuilt libraries; you're probably going to have the best luck
+building your own OBS binaries from the source. Refer to the OBS repository for more information on that.
+
+The [standard Ghostscript installers](https://www.ghostscript.com/download/gsdnld.html) do provide binary 
+libraries for linking, but they don't provide the Ghostscript header files. You may have the best luck
+downloading the binary release for the library, and then harvesting the headers from the source release. 
+You might also be okay just harvesting the necessary headers from Ghostscript's web documentation; 
+obs-ghostscript only uses two headers—[psi/api.h](https://www.ghostscript.com/doc/psi/iapi.h) and 
+[devices/gdevdsp.h](https://www.ghostscript.com/doc/devices/gdevdsp.h). If you download those individually,
+ensure that they are arranged in the proper folders.
+
+When building in CMake, you will probably need to set three configuration values so your environment can be
+properly set up:
+
+* OBSSourcePath should refer to the libobs subfolder in the OBS source release. The build pipeline will look
+  for headers in this location, and for libraries in a "build" folder relative to that path (where the OBS 
+  build process puts them). 
+* GSSourcePath should refer to the root folder of a Ghostscript source distribution (or a subset thereof 
+  containing the two aforementioned headers).
+* GSLibraryPath should refer to a folder containing the gsdll[32|64].lib binary libraries. 
+
+Note that the build pipeline will not copy the generated DLLs to an OBS Studio installation; you will need 
+to do that manually, to the locations described above. Make sure to copy the gsdll[32|64].dll from the 
+Ghostscript binary folder as well. 
+
+## License
+
+This project is licensed under the "[Unlicense](http://unlicense.org/)", because copy[right|left] is a hideous
+mess to deal with and I don't like it. 
+
+The Ghostscript binaries included in binary distributions of this project are copyright [Artifex Software, 
+Inc.](https://www.ghostscript.com/Licensing.html) and licensed under the GNU Affero General 
+Public License (AGPL). The source code is available from locations previously listed in this document. 
+Refer to the Ghostscript project's [licensing information](https://www.ghostscript.com/Licensing.html)
+for more details.