Extracting Barcodes from a Camera-Shaken Image on Camera Phones Graduate Institute of Communication Engineering National Taiwan University Chung-Hua Chu, De-Nian Yang and Ming-Syan Chen 報告者 : M97G0225 黃庭筠

OUTLINE INTRODUCTION BARCODE EXTRACTION ALGORITHM EXPERIMENTAL RESULTS CONCLUSION

INTRODUCTION problem is to extract and restore the barcode to improve the correctness of the recognition. Extracting Camera-Shaken Barcode (ECSB) algorithm for the problem

BARCODE EXTRACTION ALGORITHM

Barcode area extraction ECSB first uses Edge Detection to detect the rough barcode area as depicted. Then, ECSB dilates the edge-detected image with two directions (i.e., vertical and horizontal) such that we can obtain the precise barcode area as shown.

Barcode Restoration Use a large constant c to approximate an unknown parameter SNR (Signal to Noise Ratio), where c is larger than or equal to the height of the distorted image.

Barcode Restoration

g(i, j) = f(i, j) * h(i, j) + n(i, j) g(i, j) : presented by a linear system of a convolution f (i, j) : denotes the original image n(i, j) : defined as a Gaussian white noise with zero mean h(i, j) : (PSF) can be viewed as the filter caused by the shake

Barcode Restoration N : denotes the length of the camera motion Θ: denotes the direction of the camera motion

Camera-Shaken Direction and Length Estimation estimate the camera-shaken direction Θ : 1. first transform the camera-shaken image to a Cepstrum-domain image C (i, j) C (i, j) : Inverse Fourier transform of log(1 + G (i, j) ) G (i, j) : is the Fourier transform of g (i, j) 2. use Hough transform to find out the camera-shaken direction Θ in C (i, j)

Camera-Shaken Direction and Length Estimation camera-shaken length N : 1. calculate the average of all pixels in C' (i, j) 2. Finally, we calculate the first zero crossing where the camera-shaken length N

Camera-Shaken Direction and Length Estimation

Camera Shake Restoration Use Wiener filter to determine the solution F (i, j) Sf : power spectrum of the original image Sn : power spectrum of the noise H (i, j) : frequency domain of h (i, j) H*(i, j) : complex conjugate of H (i, j) ∣ H (i, j) ∣ ^2 : H*(i, j) H(i, j)

EXPERIMENTAL RESULTS

Tag Richardson Lucy method (TRL) : Uses tag-based identification to extract QR code, and then Richardson Lucy method (RL) to restore the extracted QR code.

EXPERIMENTAL RESULTS root mean-square error (RMSE) H : height of f (i, j) W : width of f (i, j)

EXPERIMENTAL RESULTS

CONCLUSION In this paper, we proposed an efficient algorithm to extract the 2D barcodes in a camera-shaken image. The experimental results have showed that our approach is not only of smaller running time but of higher accuracy of the barcode recognition in a mobile information environment.