  High-resolution representation learning plays an essential role in many
vision problems, e.g., pose estimation and semantic segmentation. The
high-resolution network (HRNet)~\cite{SunXLW19}, recently developed for human
pose estimation, maintains high-resolution representations through the whole
process by connecting high-to-low resolution convolutions in \emph{parallel}
and produces strong high-resolution representations by repeatedly conducting
fusions across parallel convolutions.
  In this paper, we conduct a further study on high-resolution representations
by introducing a simple yet effective modification and apply it to a wide range
of vision tasks. We augment the high-resolution representation by aggregating
the (upsampled) representations from all the parallel convolutions rather than
only the representation from the high-resolution convolution as done
in~\cite{SunXLW19}. This simple modification leads to stronger representations,
evidenced by superior results. We show top results in semantic segmentation on
Cityscapes, LIP, and PASCAL Context, and facial landmark detection on AFLW,
COFW, $300$W, and WFLW. In addition, we build a multi-level representation from
the high-resolution representation and apply it to the Faster R-CNN object
detection framework and the extended frameworks. The proposed approach achieves
superior results to existing single-model networks on COCO object detection.
The code and models have been publicly available at
\url{https://github.com/HRNet}.
