# EInk service - 1.0

EInk service contains function to work with hardware screens, displaying images, rendering and dithering.



## Configuration

Some configuration may be defined on this service :

| Environment variable       | Description                                                  | Additional informations                                      |
| -------------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ |
| SCREEN_WIDTH               | screen width                                                 | if not specified, 3200 by default                            |
| SCREEN_HEIGHT              | screen height                                                | if not specified 1800 by default                             |
| SCREEN_DISPLAY_POSITION    | display position (integer)                                   | encoded values:<br />0 : Horizontal<br />1 : Horizontal flipped<br />2: Vertical<br />3: Vertical flipped |
| SCREEN_PALETTE             | used palette (integer)                                       | encoded values:<br />0 : 25 inch eink display                |
| UNFITTED_IMAGE_DISPOSITION | in case the image does not properly fit in the screen, this define the position in the screen | 0: TopLeft<br />1: Centered                                  |
| BACKGROUND_COLOR           | color background for images that are not fitting the whole screen (default to white) |                                                              |
| EINK_DEVICE                | Eink screen driver                                           | 0: T1000<br />1: T2000<br />2 :T2000 pipelined display as eink suggest |



RQ : on cloud the given orientation is tooked : 
https://github.com/GHA-Group/e-tabelone/issues/122



Note , GPIO command, used for triggering the power on and off for the display. This can be configured on the command line. 



| Env Variable      | description                                                  |                                   |
| ----------------- | ------------------------------------------------------------ | --------------------------------- |
| GPIO_MODE         | define the usage of gpio in the display                      | 0 => no gpio, 1 => gpio activated |
| GPIO_PIN_NUMBER   | mode 1 : gpio pin number                                     |                                   |
| GPIO_DELAY_BEFORE | mode 1: gpio delay in ms to want before sending the display action |                                   |
| GPIO_DELAY_AFTER  | mode 1 : gpio delay after the display to switch off the display using the gpio |                                   |



## Detailed commands



### eink_display_draw

this function handle some image composition and additional drawing, 

| Parameter          | Description                                                  |      |
| ------------------ | ------------------------------------------------------------ | ---- |
| DRAWINGINSTRUCTION | this is a json encoded string containing the drawing commands |      |
| OUTPUTFile         | the generated output file (in .eink file format)             |      |



Drawing instruction has the following structure :

```json
{
  "base_eink_image": null,
  "empty_eink_image_configuration": {
    "width": 3200,
    "height": 1800
  },
  "instructions": []
}
```

instructions contains commands for drawing, these are described below

#### Drawing introduction

the encoded string start with a specific header telling if the drawing start from a file, or an empty white screen, with the proper width and height

one of the two `base_eink_image` or `empty_eink_image_configuration` property has to be populated. 



#### Drawing instructions

in the instructions array, one can put several instructions to make images:

| Drawing instruction |                                           | example                                                      |
| ------------------- | ----------------------------------------- | ------------------------------------------------------------ |
| DrawText            | draw a text at the specific location      | {<br/>      "DrawText": {<br/>        "text": "Hello, world!",<br/>        "color": [<br/>          255,<br/>          0,<br/>          0<br/>        ],<br/>        "x": 300,<br/>        "y": 0,<br/>        "font_size": 35,<br/>        "width": 500,<br/>        "height": 35<br/>      }<br/>    }, |
| DrawQrCode          | draw a qrcode, at a specific location,    | {<br/>      "DrawQrCode": {<br/>        "qrcode": "QRCode value",<br/>        "x": 300,<br/>        "y": 400,<br/>        "width": 100,<br/>        "height": 100<br/>      }<br/>    } |
| DrawImage           | draw a file at a specific location        |                                                              |
| DrawSvg             | draw a svg content at a specific location |                                                              |





example :

```
{
  "base_eink_image": null,
  "empty_eink_image_configuration": {
    "width": 3200,
    "height": 1800
  },
  "instructions": [
    {
      "DrawText": {
        "text": "Hello, world!",
        "color": [
          255,
          0,
          0
        ],
        "x": 300,
        "y": 0,
        "font_size": 35,
        "width": 500,
        "height": 35
      }
    },
    {
      "DrawText": {
        "text": "Hello, world!",
        "color": [
          0,
          0,
          0
        ],
        "x": 300,
        "y": 700,
        "font_size": 35,
        "width": 500,
        "height": 35
      }
    },
    {
      "DrawQrCode": {
        "qrcode": "QRCode value",
        "x": 300,
        "y": 400,
        "width": 100,
        "height": 100
      }
    }
  ]
}
```



### Sample for using the eink service using the admincli / admin_web commands



#### Redefine the screen orientation

Once the eink service is deployed, one can stop the service and reconfigure it, to change the orientation, for example : 

```
stop_app('eink-1.0')
activate_app('eink-1.0', { "SCREEN_DISPLAY_POSITION":"2" })
start_app('eink-1.0')
```

this will configure the screen in a vertical position

To check if the new parameters are properly tooked, Go to the admin_web page, and look in the deployed_applications if the parameters are correctly positionned along the "eink" application