Text Extraction from a Table Image, using PyTesseract and OpenCV

Extracting text from an image can be exhausting, especially when you have a lot to extract. One commonly known text extraction library is PyTesseract, an optical character recognition (OCR). This library will provide you text given an image.

PyTesseract is really helpful, the first time I knew PyTesseract, I directly used it to detect some a short text and the result is satisfying. Then, I used it to detect text from a table but the algorithm failed perform.

Figure 1. Direct use of PyTesseract to Detect Text in a Table

Figure 1 depicts the text detection result, with green boxes enclosing the detected words. You may realized that most of the text can’t be detected by the algorithm, especially numbers. In my case, these numbers are the essentials of the data, giving me value of daily COVID-19 cases from a local government in my hometown. So, how extract these information?

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Getting Started

When writing an algorithm, I always try to think as if I’m teaching the algorithm the way humans do. This way, I can easily put the idea into more detailed algorithms.

When you’re reading a table, the first thing you might notice is the cells. A cell might be separated from another cell using a border (lines), which can be vertical or horizontal. After you identify the cell, you proceed to read the information within. Converting it into algorithm, you may divide the process into three processes, namely cells detection, region of interest (ROI) selection, and text extraction.