Describe 2D AOI
===============

Once [frame is configured](configuration_and_execution.md), areas of interest need to be described into the same 2D referential.

![2D AOI description](../../img/aoi_2d_description.png)

According a common computer graphics coordinates convention, all AOIs need to be described from a top left frame corner origin in a coordinate system where:

* +X is pointing to the right,
* +Y is pointing to the downward.

!!! warning
	All AOIs spatial values must be given in **pixels**.

### Edit SVG file description

SVG file format could be exported from most vector graphics editors.

``` xml
<svg>
    <path id="Triangle" d="M1288.1,189.466L1991.24,3399.34L584.958,3399.34L1288.1,189.466Z"/>
    <rect id="BlueRectangle" x="1257" y="1905.18" width="604.169" height="988.564"/>
    <rect id="RedSquare" x="623.609" y="658.357" width="803.15" height="803.577"/>
    <circle id="GreenCircle" cx="675.77" cy="2163.5" r="393.109"/>
    <circle id="PinkCircle" cx="1902.02" cy="879.316" r="195.313"/>
</svg>
```

Here are common SVG file features needed to describe AOIs:  

* *id* attribute indicates AOI name.
* *path* element describes any polygon using only [M, L and Z path intructions](https://www.w3.org/TR/SVG2/paths.html#PathData)
* *rect* and *circle* allow respectively to describe rectangular and circle AOI.

### Edit JSON file description

JSON file format allows to describe AOIs.

``` json
{
    "Triangle" : [[1288.1, 189.466], [1991.24, 3399.34], [584.958, 3399.34]],
    "BlueRectangle": {
        "shape": "rectangle",
        "x": 1257,
        "y": 1905.18,
        "width": 604.169,
        "height": 988.564
    },
    "RedSquare": {
        "shape": "rectangle",
        "x": 623.609,
        "y": 658.357,
        "width": 803.15,
        "height": 803.15
    },
    "GreenCircle": {
        "shape": "circle",
        "cx": 675.77,
        "cy": 2163.5,
        "radius": 393.109
    },
    "PinkCircle": {
        "shape": "circle",
        "cx": 1902.02,
        "cy": 879.316,
        "radius": 195.313
    }
}
```