Labeling

class_index x_center y_center width height

class_index, x1, y1, x2, y2, x3, y3, x4, y4

class-index x1 y1 x2 y2 ... xn yn

class-index x y width height px1 py1 px2 py2 ... pxn pyn

class-index x y width height px1 py1 p1-visibility px2 py2 p2-visibility ... pxn pyn pn-visibility

<annotation>
    <folder>VOC2012</folder>
    <filename>image1.jpg</filename>
    <size>
        <width>800</width>
        <height>600</height>
        <depth>3</depth>
    </size>
    <object>
        <name>dog</name>
        <pose>Unspecified</pose>
        <truncated>0</truncated>
        <difficult>0</difficult>
        <bndbox>
            <xmin>48</xmin>
            <ymin>240</ymin>
            <xmax>195</xmax>
            <ymax>371</ymax>
        </bndbox>
    </object>
</annotation>

{
  "images": [
    {
      "id": 1,
      "file_name": "image1.jpg",
      "width": 800,
      "height": 600
    }
  ],
  "annotations": [
    {
      "id": 1,
      "image_id": 1,
      "category_id": 18,
      "bbox": [48, 240, 147, 131],
      "segmentation": [],
      "area": 19257,
      "iscrowd": 0
    }
  ],
  "categories": [
    {
      "id": 18,
      "name": "dog",
      "supercategory": "animal"
    }
  ]
}