OpenCV Basics

Want to combine two images using just a line of code? Or wanna blur an image? Lets find out how!

In this Article (Click to skip to that topic):

• [Blend images: What is it?]
• [Code to Blend]
• [Methods to Blur an Image ]
• [Code to Blur Image]

Blend images: What is it?

Blending images in opencv, is combining to images of same size. So we have to remember to resize those two images to same size(which will be shown in the code later).

Using this, we can make pretty cool posters, wallpapers, beautiful creations in your imaginations and many more...

So lets learn how to do it in a simple way

bigarr=np.arange(0, 10).reshape((2,5))
bigarr

#'arange' gives an array withn values from 0 to 9, 'reshapes' converts into a matrix of 2x5

Output:

array([[0, 1, 2, 3, 4],
[5, 6, 7, 8, 9]])

bigarr[:, 2]

#Here only column 2 is considered but not row as colon(:) is mentioned

Output:

array([2, 7])

For more practice on Numpy visit

 https://numpy.org/devdocs/user/quickstart.html

## Display Image in Opencv using Numpy

Now,how to open or show an image using our numpy knowledge:

We use libraries

• PIL(Python Imaging Library)

• Matplotlib( For visualization) and import Image from PIL

Image.open(image file path)       

# Opens and identifies the given image file

Each pixel has a shape.

For Eg:(1080,1080,3)which is (pixel height,pixel width,color channels)
The 3 color channels are red,green and blue(RGB).

plt.imshow                         

# Displays the image

Example

import numpy as np
import matplotlib.pyplot as plt 
%matplotlib inline
from PIL import Image

img=Image.open(r'C:\Desktop\image.jpg') 

# Opens Image

img

#To Preview Image

Each pixel has a shape.

For Eg:(1080,1080,3) which is (pixel height,pixel width,color channels).

The 3 color channels are red,green and blue(RGB).

plt.imshow             

# Displays the image

Example:

img_array=np.asarray(img)

# Converting image into array of values

img_array.shape

# Displaying the shape of the array

Output:

(1080,1920,3)

plt.imshow(img_array)

# Displaying array into Image  

What if only one channel is used in displaying image instead all 3 in RGB?

plt.imshow(array[:,:,0])           # Displays image with only Red channel.

plt.imshow(array[:,:,1])           # Displays image with only Green channel.

plt.imshow(array[:,:,2])           # Displays image with only Blue channel.

## Gray Image using Numpy

What if we want a gray image like in old movies?

The parameter cmap=’gray’ is used to convert color images into a gray image.

plt.imshow(array[:,:,0],cmap=’gray’) 

# Displays image with grayscale values.

Example

plt.imshow(img_array[:,:,0])

#Displaying only RED channel in RGB. Replace 0 with 1 for Green and 2 for Blue Channel. 

plt.imshow(img_array[:,:,0],cmap='gray')

#Converting the color image into grayscale using cmap

For more code on fliping, resizing etc visit the blog, follow the Instagram page mentioned below 😄

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