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Image Zoom

In OpenCV, the function for image scaling is: cv2.resize(InputArray src, OutputArray dst, Size, fx, fy, interpolation)

Code path:

~/dofbot_opencv/scripts/2.Transform/01_zoom_pic.ipynb

Parameter explanation:

Available interpolation methods:

Note:

1. Output size format is (width, height)
2. Default interpolation method: bilinear interpolation

Main code:

​x
# 1 load 2 info 3 resize 4 check
import cv2
import matplotlib.pyplot as plt  # Python 2D plotting library
​
# Read original image
img = cv2.imread('yahboom.jpg')
# Print image dimensions
print(img.shape)
# Assign height and width to x, y respectively
x, y = img.shape[0:2]
​
​
# Scale to half the original, output size format is (width, height)
img_test1 = cv2.resize(img, (int(y / 2), int(x / 2)))
# cv2.imshow('resize0', img_test1)
# cv2.waitKey()
​
# Nearest neighbor interpolation scaling
​
# Scale to one quarter
img_test2 = cv2.resize(img, (0, 0), fx=0.25, fy=0.25, interpolation=cv2.INTER_NEAREST)
# cv.imshow('resize1', img_test2)
# cv.waitKey()
# cv.destroyAllWindows()
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
dst1 = cv2.cvtColor(img_test1, cv2.COLOR_BGR2RGB)
dst2 = cv2.cvtColor(img_test2, cv2.COLOR_BGR2RGB)
# Display original image
plt.imshow(img)
plt.show()

After execution, you can see the image is 800*800

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# Display scaled 1/2
plt.imshow(dst1)
plt.show()

After execution, you can see the image is 400*400, scaled by half

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# Display scaled 1/4 nearest neighbor interpolation
plt.imshow(dst2)
plt.show()

After execution, you can see the image is 200*200, scaled to one quarter.

Below we talk about matplotlib: Python 2D plotting library.

Reference tutorial: https://www.runoob.com/numpy/numpy-matplotlib.html

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import numpy as np
from matplotlib import pyplot as plt
x = np.arange(1,11)
y = 2 * x + 5
plt.title("Matplotlib demo")
plt.xlabel("x axis caption")
plt.ylabel("y axis caption")
plt.plot(x,y)  
plt.show()