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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

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
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what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
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a perfect square v²+2v+_
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algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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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