  The challenges of shape robust text detection lie in two aspects: 1) most
existing quadrangular bounding box based detectors are difficult to locate
texts with arbitrary shapes, which are hard to be enclosed perfectly in a
rectangle; 2) most pixel-wise segmentation-based detectors may not separate the
text instances that are very close to each other. To address these problems, we
propose a novel Progressive Scale Expansion Network (PSENet), designed as a
segmentation-based detector with multiple predictions for each text instance.
These predictions correspond to different `kernels' produced by shrinking the
original text instance into various scales. Consequently, the final detection
can be conducted through our progressive scale expansion algorithm which
gradually expands the kernels with minimal scales to the text instances with
maximal and complete shapes. Due to the fact that there are large geometrical
margins among these minimal kernels, our method is effective to distinguish the
adjacent text instances and is robust to arbitrary shapes. The state-of-the-art
results on ICDAR 2015 and ICDAR 2017 MLT benchmarks further confirm the great
effectiveness of PSENet. Notably, PSENet outperforms the previous best record
by absolute 6.37\% on the curve text dataset SCUT-CTW1500. Code will be
available in https://github.com/whai362/PSENet.
