Seven Segments OCR


The seven_segments image processing platform allows you to read physical seven segments displays through Home Assistant. ssocr is used to extract the value shown on the display which is observed by a camera.

Home Assistant Core Requirements

If you are running Home Assistant Core in a Python virtual environment, you need to ensure the following requirements are met.

ssocr needs to be available on your system. Check the installation instruction below:

sudo dnf -y install imlib2-devel # Fedora
sudo apt install libimlib2-dev # Ubuntu
brew install imlib2 # macOS
git clone https://github.com/auerswal/ssocr.git
cd ssocr
make
sudo make PREFIX=/usr install # On most systems
make deb # (Optional) This allows you to make a deb so that you apt is aware of ssocr

Configuration

To enable the OCR of a seven segment display in your installation, add the following to your configuration.yaml file:

# Example configuration.yaml entry
image_processing:
  - platform: seven_segments
    source:
      - entity_id: camera.seven_segments

Configuration Variables

ssocr_binstring(Optional, default: ssocr)

The command line tool ssocr. Set it if you use a different name for the executable.

x_positioninteger(Optional, default: 0)

X coordinate of the upper left corner of the area to crop.

y_positioninteger(Optional, default: 0)

Y coordinate of the upper left corner of the area to crop.

heightinteger(Optional, default: 0)

Height of the area to crop.

widthinteger(Optional, default: 0)

Width of the area to crop.

rotateinteger(Optional, default: 0)

Rotation of the image.

thresholdinteger(Optional, default: 0)

Threshold for the difference between the digits and the background.

digitsinteger(Optional, default: -1)

Number of digits in the display.

extra_argumentsstring(Optional)

Other arguments to use. Like -D, dilation, erosion, greyscale, make_mono, etc.

sourcelistRequired

List of image sources.

entity_idstringRequired

A camera entity id to get picture from.

namestring(Optional)

This parameter allows you to override the name of your image_processing entity.

Setup process

It’s suggested that the first attempt to determine the needed parameters is using ssocr directly. This may require a couple of iterations to get the result

ssocr -D erosion crop 390 250 490 280 -t 20 -d 4 seven-seg.png

This would lead to the following entry for the configuration.yaml file:

camera:
  - platform: local_file
    file_path: /home/homeassistant/.homeassistant/seven-seg.png
    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

With the help of a template sensor, the value can be shown as badge.

sensor:
  - platform: template
    sensors:
      power_meter:
        value_template: '{{ states('image_processing.sevensegment_ocr_seven_segments') }}'
        friendly_name: 'Ampere'
        unit_of_measurement: 'A'