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All files referenced and other helpful information is posted on this site at the GitHub link. The GitHub link also has 3 Python files, which is our completed OCR software. This tutorial serves as a walkthrough of the code under recognitionScript.py, where more in-depth explanations are discussed in the provided .py files.

This tutorial uses Python 2.7, Numpy, and OpenCV for the software development portions. The instructions for downloading OpenCV for Linux can be found at this link. For windows, go to to opencv.org For Numpy, visit numpy.org For Python, visit python.org

We assume the reader will have been exposed to Python before. If not, a general understanding of Python IO and the ability to look up Python documentation is preferable.


For our tutorial, we will make a few assumptions for our input images. First off, the image will only have printed text. We also assume the image will be a png. For example, we will have pictures similar to the figure below. Sample image Because this is an introduction, there will not be information on transforming and translating, as this involves verbose algorithms beyond the scope of our knowledge.

Second, images may contain the full range of colors.

The first step is to read in the image we will be performing OCR on. OpenCV has the ability to do this with imread() function. We have made a wrapper function that does this and returns a copy, which will be necessary for some OpenCV functions

Reading in image

Right now, im is an image, which can be represented as a matrix with pixels. Each pixel is some object with 3 values, red, blue, green(rgb). In order to make this compatible with future functions, we will convert the image to grayscale. This involves a function provided by OpenCV, which process the rgb values and replace the pixel with some intensity value. The next step is to convert the image into grayscale. Open Cv has a color converting function called Cv2.cvtColor(image, code ) which can map one type of color to another based on the input code. For the purposes of converting our image into grayscale we use the parameter Cv2.COLOR_BGR2GRAY and call our the helper function color2gray, which returns the grayscaled image.

Convering color to gray

Greyscale Above is our grayscaled image.


Next, we will need to apply a filter onto the image. Depending on the task, we could use many different filters to achieve a certain goal. We want to filter our image to increase our ability to detect edges; this allows us to identify characters in the image. Therefore, we will be covering the Gaussian, Laplacian, and Sobel filters.

Gaussian filter

Using the following formula, we will create some n by n matrix to build the Gaussian filter.


The Gaussian filter is effective towards noisy signals, because of its characteristic as also being a low pass filter. By blurring the image to a small degree, we allow any sensitive edge detection algorithms to not mistake noise to be something of significance.


In cases where we know that noise is not an issue, we can use the Laplacian filer. Rather than worry about reducing noise, the Laplace filter's purpose is to enhance edges by sharpening the image. The formula to describe the filter is

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Introduction to optical character recognition. OpenStax CNX. Dec 17, 2014 Download for free at http://legacy.cnx.org/content/col11728/1.1
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