8CNNs for Optical Character Recognition
8.1 Introduction
Optical character recognition (OCR) is the process of digitizing and recognizing images of written, typed or printed text [78]. A typical example of OCR usage is postal automation, where letters and packages are classified based on their hand‐written or typed addresses and labels. Rather than manually reading and typing the address of each letter into a computer, OCR allows the computer to recognize and process the addresses automatically. Other applications of OCR include capturing licence plate numbers, conversion of physical documents to editable text documents and assistance for the blind and visually impaired. A popular information source used for OCR is the MNIST dataset [79]. It consists of 70 000 greyscale images of handwritten numerical digits ranging from 0 to 9. Each digit is stored as a
pixel image. The dataset is divided into 60 000 training samples and 10 000 test samples. Figure 8.1a displays a few examples from the MNIST dataset [80]. The MNIST website contains the performance of various classification methods trained on the dataset. It is reported on the MNIST website that CNNs currently outperform every other classifier for character recognition applications. In Figure 8.1b, the lowest error rate corresponding to each classifier is listed.
Figure 8.1 Essential information for OCR applications in MNIST ...
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