  Scene text detection is a challenging computer vision task due to the high
variation in text shapes and ratios. In this work, we propose a scene text
detector named Deformable Kernel Expansion (DKE), which incorporates the merits
of both segmentation and contour-based detectors. DKE employs a segmentation
module to segment the shrunken text region as the text kernel, then expands the
text kernel contour to obtain text boundary by regressing the vertex-wise
offsets. Generating the text kernel by segmentation enables DKE to inherit the
arbitrary-shaped text region modeling capability of segmentation-based
detectors. Regressing the kernel contour with some sampled vertices enables DKE
to avoid the complicated pixel-level post-processing and better learn contour
deformation as the contour-based detectors. Moreover, we propose an Optimal
Bipartite Graph Matching Loss (OBGML) that measures the matching error between
the predicted contour and the ground truth, which efficiently minimizes the
global contour matching distance. Extensive experiments on CTW1500, Total-Text,
MSRA-TD500, and ICDAR2015 demonstrate that DKE achieves a good tradeoff between
accuracy and efficiency in scene text detection.
