Seven segments OCR image processing

[fabaff]

Description:

An image is processed with ssocr to extract the value shown on a seven segments display.

This is requires that ssocr is available on the system that runs Home Assistant. It's not an "add-and-you-are-good-to-go" platform, it could require a lot of iterations to get the configuration entries, especially threshold.

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#2655

Example entry for configuration.yaml (if applicable):

camera:
  - platform: local_file
    file_path: /home/fab/.homeassistant/test/ss-test.jpg
    name: seven_segments
image_processing:
  - platform: seven_segments
    x_position: 390
    y_position: 250
    height: 280
    width: 490
    threshold: 20
    digits: 4
    source:
      - entity_id: camera.seven_segments

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies are only imported inside functions that use them ([example][ex-import]).
• New files were added to .coveragerc.

[mention-bot]

@fabaff, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @pvizeli and @happyleavesaoc to be potential reviewers.