1. Introduction
Text is the most fundamental medium for communicating semantic information. It appears everywhere in daily life: on street nameplates, store signs, product packages, restaurant menus and so on. Such texts in natural environment are known as scene texts. Automatically detecting and recognizing scene texts can be very rewarding with numerous applications, such as real-time text translation, blind person assistance, shopping, robots, smart cars and education. An end-to-end text recognition system usually consists of two steps: text detection and text recognition. In text detection, text regions are detected and labeled with their bounding boxes. And in text recognition, text information is retrieved from the detected text regions. Text detection is an important step for end-to-end text recognition, without which texts can not be recognized from scene images. Therefore, scene text detection attracts much attention these years.