Road Sign Recognition System Based on GentleBoost with Sharing Features Jin-Yi Wu, Chien-Chung Tseng,Chun-Hao Chang, Jenn-Jier James Lien*, Ju Chin Chen, Ching Ting Tu ICSSE 2011

Outline Goal Method Experimental Result Future work Detection Module Recognition Module Experimental Result Future work

Goal Guide the driver to drive in the correct lane and at the right speed. support the driver during the tedious task of remembering the large number of road signs.

Flowchart

Method: two modules Detection Module Recognition Module Stage 1:Color-Based, finding sign candidates. Stage 2:Shap-Based, Classification. Recognition Module Stage 1: GenteBoost with Sharing Features Stage 2: Rotation, scale, translation invariant

Detection Module Stage 1: Color-Based Segmentation Road signs are designed using colors to reflect it’s message. These colors stand out from the environment.

HIS color space hue saturation intensity (HSI) domain are sufficient to isolate road signs in a scene. [4] S. M. Bascon, S. L. Arroyo, P. G. Jimenez, H. G. Moreno, F. L. Ferreras, "Road-Sign Detection and Recognition Based on Support Vector Machines", IEEE Transaction Intelligent Transportation Systems, vol. 8, no. 2, pp. 264-278, 2007.

Threshold the response to varying wavelength and intensity of standard imaging is nonlinear and interdependent. The database GRAM and other image are used to train the suitable threshold.

Candidate selection Each connected object is called a blob. A candidate blob must laeger than 30x30. aspect ratio is delimited between 1.9 and 1/1.9(suggested in [4]) [4] S. M. Bascon, S. L. Arroyo, P. G. Jimenez, H. G. Moreno, F. L. Ferreras, "Road-Sign Detection and Recognition Based on Support Vector Machines", IEEE Transaction Intelligent Transportation Systems, vol. 8, no. 2, pp. 264-278, 2007.

Detection Module Stage 2: Shape-Based Classification Then Distance to borders (DtBs) feature and linear Support Vector Machine (SVM) are used to classify the shape of the blobs as [4]. [4] S. M. Bascon, S. L. Arroyo, P. G. Jimenez, H. G. Moreno, F. L. Ferreras, "Road-Sign Detection and Recognition Based on Support Vector Machines", IEEE Transaction Intelligent Transportation Systems, vol. 8, no. 2, pp. 264-278, 2007.

linear SVM Database GRAM and other image. DtBs result. Classify the blobs into a certain shape, i.e. circular, triangular, rectangular shapes.

Method: two modules Detection Module Recognition Module Stage 1:Color-Based, finding sign candidates. Stage 2:Shap-Based, Classification. Recognition Module Stage 1: GenteBoost with Sharing Features Stage 2: Rotation, scale, translation invariant

Recognition Module Stage 1: GenteBoost with Sharing Features Use weak classifiers to form a stronger classifier.

Road sign database 30 x 30 pixel. 108 road signs: 48 red triangular signs 36 red circular signs 15 blue circular signs 9 blue rectangular signs

Chromatic parts(1/2) 20x20-pixel. 5 types of red circular. used for ensuring the existence of the road signs. type1 type2 Type3,4,5

Chromatic parts(2/2) if the chromatic part matches one of the types, we lower the threshold for the according type in RST-Invariant template matching due to the high probability that road sign in the same type may appear.

Rotation, scale, translation invariant (RST-invariant) Red road signs: Simply match the middle part of candidate blob(20x20-pixel). The thresholds is adjusted by the result from the GentleBoost detector.(only red circular signs) Blue road signs: Simply match the complete candidate blob (30x30-pixel).

Step 1: Circular sampling filter (Cifi) R is the radius of the template. Corr = correlation Ti is ith templates with the same shape If the Corr value is larger than a threshold tc, the template Ti is passed to second step, otherwise, Ti will be discard. C(x, y)={C(x, y, r), r = 1 to R}

Step 2: Radial sampling filter (Rafi) α is inclianation of Radial line, l is length of Radial line. “cshiftj” means circular shifting j positions of the argument vector. If Corr value is larger than a threshold tr, the template Tk will be rotated with the corresponding angle and passed to the final step. R(x,y) = R(x,y,α), α = 0 ~ 360}

Step 3: template matching filter step Corresponding with template which pass the step2 ? There is no detail mention in this paper ?

Thresholds tc=0.9, tr=0.9, and tm=0.8 tc=0.5, tr=0.5,and tm=0.45 for the corresponding type of the candidate blob.

Experimental result(1/2) The detection rate and the false alarm rate for road signs in GRAM database, which is also used in [27] and [28], is 80.4% and 45.4, respectively. 632 images for Experimental. [27] P. Gil-Jimenez, S. Lafuente-Arroyo, H. Gomez-Moreno, F. Lopez- Ferreras, and S. Maldonado-Bascon,” Traffic Sign Shape Classification Evaluation II : FFT Applied to The Sognature of Blobs,” in Proceedings of IEEE Intelligent Vehicles Symposium, pp. 607-612, 2005. [28] S. Lafuente-Arroyo, P. Gil-Jimenez, R. Maldonado-Bascon ,” Traffic Sign Shape Classification Evaluation I : SVM Using Distance to Broders,” in Proceedings of IEEE Intelligent Vehicles. Symposium, pp. 557-562, 2005.

Experimental result(2/2)

This work… able to accurately classify different shapes of road signs in difficult conditions.(rotations, scaling, translations, and even partial occlusions.) can run in almost real-time with 720x480-pixel image with average 12 fps on a 3.0-GHz CPU.

Future work to improvements Same false alarm usually will not appear in adjacent frames. Using different feature rather than DtBs in shape classification. Extended to detect some other kinds of signboards such as signs of gas station or convenient shop