Add global readme with guides on how to generate photos

ad-si · Feb 2, 2018 · 957f28e · 957f28e
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+# Perspectra
+
+Extract and perspectively correct documents in images.
+
+Check out [github:adius/awesome-scanning]
+for and extensive list of alternative solutions.
+
+[github:adius/awesome-scanning]: https://github.com/adius/awesome-scanning
+
+
+## Best Practices for Taking the Photos
+
+TODO
+
+
+## Generating the Photos from a Video
+
+A good tool for this purpose is [PySceneDetect].
+It's a Python/OpenCV-based scene detection program,
+using threshold/content analysis on a given video.
+
+[PySceneDetect]: https://github.com/Breakthrough/PySceneDetect
+
+For easy installation you can use the [docker image]
+
+[docker image]: https://github.com/handflucht/PySceneDetect
+
+
+Find good values for threshold:
+
+```fish
+docker run \
+  --rm \
+  --volume (pwd):/video \
+  handflucht/pyscenedetect
+  --input /video/page-turning.mp4 \
+  --downscale-factor 2 \
+  --detector content \
+  --statsfile page-turning-stats.csv
+```
+
+
+To launch the image run:
+
+```fish
+docker run \
+  --interactive \
+  --tty \
+  --volume=(pwd):/video \
+  --entrypoint=bash \
+  handflucht/pyscenedetect
+```
+
+
+Then run in the shell:
+
+```bash
+cd /video
+scenedetect \
+  --input page-turning.mp4 \
+  --downscale-factor 2 \
+  --detector content \
+  --min-scene-length 50 \
+  --threshold 3 \
+  --save-images
+```
+
+
+TODO: The correct way to do this:
+(after https://github.com/Breakthrough/PySceneDetect/issues/45 is implemented)
+
+```fish
+docker run \
+  --rm \
+  --volume (pwd):/video \
+  handflucht/pyscenedetect \
+  --input /video/page-turning.mp4 \
+  --downscale-factor 2 \
+  --detector content \
+  --threshold 5 \
+  --save-images <TODO: path>
+```
+
+
+Aim for a low threshold and a long minimun scene length.
+I.e. turn the page really fast and show it for a long time.