Title :
Affine-invariant recognition of gray-scale characters using global affine transformation correlation
Author :
Wakahara, Toru ; Kimura, Yoshimasa ; Tomono, Akira
Author_Institution :
NTT Cyber Solutions Lab., Nippon Telegraph & Telephone Corp., Kanagawa, Japan
fDate :
4/1/2001 12:00:00 AM
Abstract :
Describes a technique of gray-scale character recognition that offers both noise tolerance and affine-invariance. The key ideas are twofold. First is the use of normalized cross-correlation as a matching measure to realize noise tolerance. Second is the application of global affine transformation (GAT) to the input image so as to achieve affine-invariant correlation with the target image. In particular, optimal GAT is efficiently determined by the successive iteration method using topographic features of gray-scale images as matching constraints. We demonstrate the high matching ability of the proposed GAT correlation method using gray-scale images of numerals subjected to random Gaussian noise and a wide range of affine transformation. Moreover, extensive recognition experiments show that the achieved recognition rate of 94.3 percent against rotation within 30 degrees, scale change within 30 percent, and translation within 20 percent of the character width along with random Gaussian noise is sufficiently high compared to the 42.8 percent offered by simple correlation
Keywords :
Gaussian noise; correlation methods; image matching; iterative methods; optical character recognition; affine-invariant correlation; affine-invariant recognition; global affine transformation; global affine transformation correlation; gray-scale characters; matching constraints; noise tolerance; normalized cross-correlation; random Gaussian noise; successive iteration method; topographic features; Character recognition; Degradation; Gaussian noise; Gray-scale; Image matching; Image recognition; Image segmentation; Shape; Surface morphology; Surface topography;
Journal_Title :
Pattern Analysis and Machine Intelligence, IEEE Transactions on