doc: README

_dist/README.txt

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+A thumbnailing library for Go.
+
+Written in Go
+
+Earlier versions of this project were vendored into `webdir`.
+
+- Supports jpeg / png / gif files (internally) and video files (requires `ffmpeg` in `$PATH`)
+- LRU cache of recent thumbnails for performance
+- Scaling algorithms: Nearest-neighbour or bilinear
+- Aspect ratio preserving (fit outside with image crop; fit inside with transparent background; fit inside with dimension reduction)
+- Output formats: JPG (internal) or transparent PNG (via `go-imagequant`)
+
+A standalone binary `mkthumb` is provided as a sample utility.
+
+=CHANGELOG=
+
+20??-??-?? 0.2.0
+- Initial standalone release
+- Feature: Decode input with specified mime type
+- Feature: Allow passing zero as thumbnail cache size
+
+2017-01-03 webdir-1.0
+- Included with `webdir`