<p>The simple answer is no. This framework based on <a href="https://arxiv.org/abs/1506.01497" rel="nofollow noreferrer">Faster R-CNN: Towards Real-Time Object Detection with Region Proposal Networks</a> and <a href="https://arxiv.org/abs/1512.02325" rel="nofollow noreferrer">SSD: Single Shot MultiBox Detector</a> which train additional output of CNN for <strong>bounding box</strong> regression. Can you create CNN with some structure for detect polygon instead of bounding box? May be, but whis will another network.</p>
TensorFlow object detection other shape of classification
<p>in TensorFlow object detection API, is there any possibility to get other shape of recognized object than rectangle? </p>

<p>For example when I'm teaching my computer to recognize a forest, mostly it should be more useful to get some kind of polygon instead of rectangle. </p>

<p>Other thing is for example river, but polygon seems much easier than line. </p>