Seven segments (#2655)

* Add seven-segments platform docs

* Add screenshot

source/_components/image_processing.seven_segments.markdown

@@ -0,0 +1,92 @@
+---
+layout: page
+title: "Seven segments display"
+description: "Instructions how to use OCR for seven segemnts displays into Home Assistant."
+date: 2017-05-18 08:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: Image Processing
+featured: false
+ha_release: 0.45
+---
+
+The `seven_segments` image processing platform allows you to read physical seven segments displays through Home Assistant. [`ssocr`](https://www.unix-ag.uni-kl.de/~auerswal/ssocr/) is used to extract the value shown on the display which is observed by a [camera](/components/camera/). `ssocr` need to be available on your system. Check the installation instruction for Fedora below or use `$ sudo apt-get install ssocr` on a Debian-based system:
+
+```bash
+$ sudo dnf -y install imlib2-devel
+$ git clone https://github.com/auerswal/ssocr.git
+$ cd ssocr
+$ make
+$ sudo make PREFIX=/usr install
+```
+
+To enable the OCR of a seven segement display in your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+image_processing:
+  - platform: seven_segments
+    source:
+      - entity_id: camera.seven_segments
+```
+
+Configuration variables:
+
+- **ssocr_bin** (*Optional*): The command line tool `ssocr`. Set it if you use a different name for the executable. Defaults to `ssorc`.
+- **x_position** (*Optional*): X coordinate of the upper left corner of the area to crop. Defaults to `0`.
+- **y_position** (*Optional*):  Y coordinate of the upper left corner of the area to crop. Defaults to `0`.
+- **height** (*Optional*): Height of the area to crop. Defaults to `0`.
+- **width** (*Optional*): Width of the area to crop. Defaults to `0`.
+- **threshold** (*Optional*): Threshold for the difference between the digits and the background. Defaults to `0`.
+- **digits** (*Optional*): Number of digits in the display. Defaults to `-1`.
+- **source** array (*Required*): List of image sources.
+  - **entity_id** (*Required*): A camera entity id to get picture from.
+  - **name** (*Optional*): This parameter allows you to override the name of your `image_processing` entity.
+
+
+### {% linkable_title 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
+
+```bash
+$ ssocr -D erosion crop 390 250 490 280 -t 20 -d 4 ss-test.jpg
+```
+
+This would lead to the following entry for the `configuration.yaml` file:
+
+```yaml
+camera:
+  - platform: local_file
+    file_path: /home/fab/.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
+```
+
+<p class='img'>
+  <img src='{{site_root}}/images/screenshots/ssocr.png' />
+</p>
+
+With the help of a [template sensor](/components/sensor.template/), the value can be shown as badge.
+
+```yaml
+sensor:
+  - platform: template
+    sensors:
+      power_meter:
+        value_template: '{{ states.image_processing.sevensegement_ocr_seven_segments.state }}'
+        friendly_name: 'Ampere'
+        unit_of_measurement: 'A'
+```
+