Scale and skew-invariant road sign recognition

Yi Sheng Liu, Der Jyh Duh, Shu Yuan Chen*, Ru Sheng Liu, Jun-Wei Hsieh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


A fast and robust method to detect and recognize scaled and skewed road signs is proposed in this paper. In the detection stage, the input color image is first quantized in HSV color model. Border tracing those regions with the same colors as road signs is adopted to find the regions of interest (ROI). The ROIs are then automatically adjusted to fit road sign shape models so as to facilitate detection verification even for scaled and skewed road signs in complicated scenes. Moreover, the ROI adjustment and verification are both performed only on border pixels; thus, the proposed road sign detector is fast. In the recognition stage, the detected road sign is normalized first. Histogram matching based on polar mesh is then adopted to measure the similarity between the scene and model road signs to accomplish recognition. Since histogram matching is fast and has high tolerance to distortion and deformation while contextual information can still be incorporated into it in a natural and elegant way, our method has high recognition accuracy and fast execution speed. Experiment results show that the detection rate and recognition accuracy of our method can achieve 94.2% and 91.7%, respectively. On an average, it takes only 4-50 and 10 ms for detection and recognition, respectively. Thus, the proposed method is effective, yet efficient.

Original languageEnglish
Pages (from-to)28-39
Number of pages12
JournalInternational Journal of Imaging Systems and Technology
Issue number1
StatePublished - 3 Aug 2007


  • Border tracing
  • Color quantization
  • Histogram matching
  • HSV color model
  • Polar mesh
  • Road sign detection
  • Road sign recognition


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