How Does Optical Character Recognition Work?

By NE Docs | April 24, 2014

Optical character recognition, or OCR, is a process which allows us to convert text based images into editable electronic documents. These images can be produced by scanners, cameras, read only files, etc. In our last article – What is OCR – we discussed the basics of Optical Character Recognition software and took a brief look at its origins. However, there is one fundamental piece to OCR technology that we did not cover. How does it work?

How Optical Character Recognition Works:

Optical character recognition software takes several steps to convert an image file into an editable document. Each step in this process uses a specific algorithm to alter, enhance, and interpret the images found within a file. Each and every step involved in this process is critical to the overall success of OCR. Even the smallest error will cause major issues, resulting in a poorly translated final document. 

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The OCR Process:

Step 1 – Loading the image file: In order for OCR to be effective, it must support a wide array of file formats, including PDF, BMP, TIFF, JPEG, and PNG files. Once the file is loaded, the software can begin to work. These files can be scanned documents, photographs, or even read-only files. Regardless of the original format, OCR software will transform these files into easily accessible & editable data.

Step 2 – Improving image quality and orientation: Depending on the method in which the image file was created, there are a number of issues that may arise. More often than not, an image file will be skewed or contain “noise” (a/k/a varying brightness or color). In this stage of OCR, the software will work to de-skew, remove any “noise”, and improve the overall quality of the images. This is a critical step – as blurry or skewed images are not interpreted properly.

Step 3 – Removing lines: Lines can prove to be disastrous when interpreting characters. In order to remain as accurate as possible – lines are detected and removed. This allows for better recognition quality when converting tables, underlined words, etc. Much like the importance of image quality, the removal of lines will ensure that characters are recognized accurately.

Step 4 – Analyzing the page: During this stage of Optical Character Recognition, the layout of the original file is noted and processed. This includes the detection of text positions, white space, and the prioritization of important text areas or sections.

Step 5 – Detecting words and lines of text: This is the beginning stage of actual character recognition. The software begins to identify individual words and entire lines of data. This is a critical pre-process for properly recognizing characters as it sets the stage for the analysis and correction of broken or merged characters.

Step 6 – Analyzing and fixing of “broken” or “merged” characters: Depending on the quality of the original file, there are often errors in which characters are broken or blurred together. The OCR software must now break down and resolve these errors in order to properly interpret the appropriate characters.

Step 7 – Recognizing characters: This is the primary function of Optical Character Recognition. Now that the original file has been processed, cleaned, and fixed – the OCR technology can begin to read and translate characters. Each image of every character is converted into a character code. If the algorithm is unsure of a character – the software will produce multiple character codes and choose the proper character later on.

Step 8 – Saving the file: After the file has been fully interpreted, it can be saved to your desired file format. While there is much more to OCR software, these 8 steps make up the primary processes involved in Optical Character Recognition.

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