Monthly Archives: October 2018

Week 3 – Drawing on images & Thresholding

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This week we performed further image manipulation in the form of adding, circles and lines and borders on images loaded into OpenCV. We also looked into Threholding and were introduced to the Histogram in relation to image Processing.

Code for the lab tasks.

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# 1. Open a user-selected image;
 
# 2. Show this image on the screen;
 
# 3. Capture the user’s click on the image;
 
import numpy as np
import cv2
from matplotlib import pyplot as plt
from matplotlib import image as image
import easygui
 
I = cv2.imread("colors.jpg")
 
Original = I.copy()
 
def draw(event,x,y,flags,param):
if event == cv2.EVENT_LBUTTONDOWN:
cv2.circle(img = I, center = (x,y),radius = 5, color = (255,255,255), thickness = -1)
cv2.imshow("image", I)
cv2.namedWindow("image")
cv2.setMouseCallback("image", draw)
cv2.imshow("image", I)
key = cv2.waitKey(0)

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# 4. Draw a 201 x 201, 5-pixel thick red square around this location;
 
# 5. Convert the pixels within the square to YUV.
 
import numpy as np
import cv2
from matplotlib import pyplot as plt
from matplotlib import image as image
import easygui
 
I = cv2.imread("colors.jpg")
 
YUV = cv2.cvtColor(I, cv2.COLOR_BGR2YUV)
 
cv2.rectangle(img = I, pt1 = (4,4), pt2 = (270,177), color = (0,0,255), thickness = 10)
 
cv2.imshow("image", I)
key = cv2.waitKey(0)