title: How to impelement post-proccesing for yolo v3 or v4 onnx models in ML.Net
body: <p>I followed <a href="https://docs.microsoft.com/en-us/dotnet/machine-learning/tutorials/object-detection-onnx" rel="nofollow noreferrer">this microsoft tutorial</a> and there was no problem. but i wanted to change model to yolo v3 or v4. I get the YOLOv4 onnx model from <a href="https://github.com/onnx/models/tree/master/vision/object_detection_segmentation/yolov4" rel="nofollow noreferrer">onnx/models</a> and was able to get all three array of float outputs of yolov4 onnx model but the problem is with post-processing and i can't get proper boundinboxes from these outputs.</p>
  <p>I changed all things like anchors, strides, output grid sizes, some functios and... in microsoft tutorial src code to be compatible with yolov4.  but I cant get proper results.
  I checked all my code with <a href="https://github.com/onnx/models/tree/master/vision/object_detection_segmentation/yolov4" rel="nofollow noreferrer">python implementation</a> but i don't know where is the problem.
  Does anyone have a link or knows how to implement yolo v3 or v4 onnx models in c# with ML.Net</p>
  <p>Any help will be appreciated</p>