add README.md

README.md

@@ -0,0 +1,30 @@
+# Oh-My-Stitcher
+
+## How to build
+
+1. Clone this repo (obviously)
+2. Enter repo (solution) directory
+3. `dotnet build`
+
+## How to run
+
+0. This project uses ASP.Net AoT, please don't forget to install `zlib1g-dev`.
+
+1. Publish it
+  - Enter `src/Oh.My.Stitcher`
+  - `dotnet publish -c Release -r linux-arm64`
+
+2. Run it
+  - Enter `src/Oh.My.Stitcher/bin/Release/net8.0/linux-arm64/publish`
+  - `ASSET_PATH_RO=/path/to/tiles ./Oh.My.Stitcher`
+
+## Caching
+
+For better performance, this stitcher use caching mechanism. The full image size would be GigaBytes!!!, so
+the cache is limited, max size that can be cached: 720 x 720 x 128 (approximately 70MB).
+It uses OS temporary directory (`Path.GetTempPath` or `/tmp`), please make sure it's writable.
+
+No, this doesn't break the rule, the cache is created and used AFTER the first API request.
+
+Use cases:
+- consecutive request with the same rect and scale (e.g. "A1:AE55" then "AE1:A55")