add export roLabelImg format

[fanweiya]

Because labelstudio already support label ROTATED rectangle regions whether it can support the exported roLabelImg format

<annotation verified="yes">
  <folder>hsrc</folder>
  <filename>100000001</filename>
  <path>/Users/haoyou/Library/Mobile Documents/com~apple~CloudDocs/OneDrive/hsrc/100000001.bmp</path>
  <source>
    <database>Unknown</database>
  </source>
  <size>
    <width>1166</width>
    <height>753</height>
    <depth>3</depth>
  </size>
  <segmented>0</segmented>
  <object>
    <type>bndbox</type>
    <name>ship</name>
    <pose>Unspecified</pose>
    <truncated>0</truncated>
    <difficult>0</difficult>
    <bndbox>
      <xmin>178</xmin>
      <ymin>246</ymin>
      <xmax>974</xmax>
      <ymax>504</ymax>
    </bndbox>
  </object>
  <object>
    <type>robndbox</type>
    <name>ship</name>
    <pose>Unspecified</pose>
    <truncated>0</truncated>
    <difficult>0</difficult>
    <robndbox>
      <cx>580.7887</cx>
      <cy>343.2913</cy>
      <w>775.0449</w>
      <h>170.2159</h>
      <angle>2.889813</angle>
    </robndbox>
  </object>
</annotation>

[makseq]

@fanweiya Is it subset of VOC format? Or it's different.

[fanweiya]

@fanweiya是 VOC 格式的子集吗？或者情况不同。

Yes,This is a format for rotating target detection.https://github.com/cgvict/roLabelImg

[glenbhermon]

You could give an option selector to include rotation within the VOC format, within the export options. It will be really helpful! Thanks for all the work thus far!