Tag Archives: cv2.waitKey()

Creating a Bouncing Ball Screensaver using OpenCV-Python

Task:

Create a Window that we can write text on. If we don’t write for 10 seconds screensaver will start.

For this we need to do two things:

First, we need to check whether a key is pressed in the specified time. Here, I have used 10 sec.
Second, create a bouncing ball screensaver and display it only if no key is pressed in the specified time, otherwise, display the original screen.

The first part can be done using the OpenCV cv2.waitKey() function which waits for a specific time for a key press (See here for more details).

For the second part, we first need to create a bouncing ball screensaver. The main idea is to change the sign of increment (dx and dy in the code below) on collision with the boundaries. This can be done using the following code

def screensaver():
    img = np.zeros((480,640,3),dtype='uint8')
    dx,dy =1,1
    x,y = 100,100
    while True:
        # Display the image
        cv2.imshow('a',img)
        k = cv2.waitKey(10)
        img = np.zeros((480,640,3),dtype='uint8') 
        # Increment the position
        x = x+dx
        y = y+dy
        cv2.circle(img,(x,y),20,(255,0,0),-1)
        if k != -1:
            break
        # Change the sign of increment on collision with the boundary
        if y >=480:
            dy *= -1
        elif y<=0:
            dy *= -1
        if x >=640:
            dx *= -1
        elif x<=0:
            dx *= -1
    cv2.destroyAllWindows()

def screensaver():

img = np.zeros((480,640,3),dtype='uint8')

dx,dy =1,1

x,y = 100,100

while True:

# Display the image

cv2.imshow('a',img)

k = cv2.waitKey(10)

img = np.zeros((480,640,3),dtype='uint8')

# Increment the position

x = x+dx

y = y+dy

cv2.circle(img,(x,y),20,(255,0,0),-1)

if k != -1:

break

# Change the sign of increment on collision with the boundary

if y >=480:

dy *= -1

elif y<=0:

dy *= -1

if x >=640:

dx *= -1

elif x<=0:

dx *= -1

cv2.destroyAllWindows()

The snapshot of the screensaver looks like this

Now, we need to integrate this screensaver function with the cv2.waitKey() function as shown in the code below

import cv2
import numpy as np
# Background Image
img1 = cv2.imread('D:/downloads/original_image.png')
# Initialize these for text placement
i = 0 
a,b = 30,30
while True:
    cv2.imshow('a',img1)
    k = cv2.waitKey(10000)
    # If no key is pressed, display the screensaver
    if k == -1:
        screensaver()
    # Press Escape to exit
    elif k == 27:
        break
    # Otherwise write real time text on the image.
    # This is used for visualization only
    # You can use anything here.
    else:
        font = cv2.FONT_HERSHEY_SIMPLEX
        cv2.putText(img1,chr(k),(a+i,b), font, 0.5,(255,255,255),2,cv2.LINE_AA)
        if a+i >= img1.shape[1]:
            b = b+15
            i = 0
        i +=10
        
cv2.destroyAllWindows()

import cv2

import numpy as np

# Background Image

img1 = cv2.imread('D:/downloads/original_image.png')

# Initialize these for text placement

i = 0

a,b = 30,30

while True:

cv2.imshow('a',img1)

k = cv2.waitKey(10000)

# If no key is pressed, display the screensaver

if k == -1:

screensaver()

# Press Escape to exit

elif k == 27:

break

# Otherwise write real time text on the image.

# This is used for visualization only

# You can use anything here.

else:

font = cv2.FONT_HERSHEY_SIMPLEX

cv2.putText(img1,chr(k),(a+i,b), font, 0.5,(255,255,255),2,cv2.LINE_AA)

if a+i >= img1.shape[1]:

b = b+15

i = 0

i +=10

cv2.destroyAllWindows()

You need to set the size of the screensaver and background image to be the same. The output looks like this

Hope you enjoy reading.

If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.

Show current DateTime on live video using OpenCV-Python

1 Reply

Have you seen the security cameras output where DateTime continuously keeps updating? In this blog, we will be doing the same using OpenCV-Python i.e. we will put current DateTime on the live webcam feed. So, let’s get started.

For fetching current DateTime, we will be using Python’s DateTime module. The following code shows how to get the current DateTime

# get current DateTime
from datetime import datetime
print(datetime.now())

# get current DateTime

from datetime import datetime

print(datetime.now())

To put the DateTime on the live video, we will be using cv2.putText() on each frame as shown below

# Put current DateTime on each frame
cv2.putText(img,str(datetime.now()),(140,250), font, .5,(255,255,255),2,cv2.LINE_AA)

1 2	# Put current DateTime on each frame cv2.putText(img,str(datetime.now()),(140,250), font, .5,(255,255,255),2,cv2.LINE_AA)

To know more about cv2.putText(), refer to this blog.

Above are the two things, that we will be needing for this task. I hope you understand these. Now, let’s get started

Steps:

Open the camera using cv2.VideoCapture()
Until the camera is open
- Grab each frame using cap.read()
- Put the current DateTime on each frame using cv2.putText() as discussed above
- Display each frame using cv2.imshow()
On termination, release the webcam and destroy all windows using cap.release() and cv2.destroyAllWindows() respectively.

Code:

import cv2
from datetime import datetime
# Open the Camera
cap = cv2.VideoCapture(0)
while True:
    ret, img = cap.read()
    # Put current DateTime on each frame
    font = cv2.FONT_HERSHEY_SIMPLEX
    cv2.putText(img,str(datetime.now()),(10,30), font, 1,(255,255,255),2,cv2.LINE_AA)
    # Display the image
    cv2.imshow('a',img)
    # wait for keypress
    k = cv2.waitKey(10)
    if k == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

import cv2

from datetime import datetime

# Open the Camera

cap = cv2.VideoCapture(0)

while True:

ret, img = cap.read()

# Put current DateTime on each frame

font = cv2.FONT_HERSHEY_SIMPLEX

cv2.putText(img,str(datetime.now()),(10,30), font, 1,(255,255,255),2,cv2.LINE_AA)

# Display the image

cv2.imshow('a',img)

# wait for keypress

k = cv2.waitKey(10)

if k == ord('q'):

break

cap.release()

cv2.destroyAllWindows()

The snapshot of the output looks like this

Hope you enjoy reading.

If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.

Write Text on images in real-time using OpenCV-Python

Steps:

Read the image and initialize the counter that will be used for changing the position of the text.
Inside an infinite while loop,
- display the image and use cv2.waitKey() for a keypress.
- Convert this key into character using chr() and draw it on the image using cv2.putText().
- Increase the counter.
- Provide the termination condition
On exit, destroy all windows.

Below is the code for this

import cv2
# Read the image
img = cv2.imread('D:/downloads/original_image.png')
# initialize counter
i = 0
while True:
    # Display the image
    cv2.imshow('a',img)
    # wait for keypress
    k = cv2.waitKey(0)
    # specify the font and draw the key using puttext
    font = cv2.FONT_HERSHEY_SIMPLEX
    cv2.putText(img,chr(k),(140+i,250), font, .5,(255,255,255),2,cv2.LINE_AA)
    i+=10
    if k == ord('q'):
        break
cv2.destroyAllWindows()

import cv2

# Read the image

img = cv2.imread('D:/downloads/original_image.png')

# initialize counter

i = 0

while True:

# Display the image

cv2.imshow('a',img)

# wait for keypress

k = cv2.waitKey(0)

# specify the font and draw the key using puttext

font = cv2.FONT_HERSHEY_SIMPLEX

cv2.putText(img,chr(k),(140+i,250), font, .5,(255,255,255),2,cv2.LINE_AA)

i+=10

if k == ord('q'):

break

cv2.destroyAllWindows()

The output looks like this

Hope you enjoy reading. In the next blog, we will learn how to write text on images at mouse click position.

If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.

Write Text on images at mouse click position using OpenCV-Python

Steps:

Create a mouse callback function where on every left double click position we put text on the image.
Create or read an image.
Create an image window using cv2.namedWindow()
Bind the mouse callback function to the image window using cv2.setMouseCallback()
Display the new image using an infinite while loop

Code:

import cv2
import numpy as np

font = cv2.FONT_HERSHEY_SIMPLEX
# mouse callback function
def draw_circle(event,x,y,flags,param):
    if event == cv2.EVENT_LBUTTONDBLCLK:
        i = 0
        while True:
            cv2.imshow('image',img) # to display the characters
            k = cv2.waitKey(0)
            cv2.putText(img, chr(k) , (x+i,y), font, 0.5, (0, 255, 0), 2, cv2.LINE_AA)
            i+=10
            # Press q to stop writing
            if k == ord('q'):
                break

    

# Create a black image, a window and bind the function to window
img = np.zeros((512,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)

while True:
    cv2.imshow('image',img)
    if cv2.waitKey(20) == 27:
        break
cv2.destroyAllWindows()

import cv2

import numpy as np

font = cv2.FONT_HERSHEY_SIMPLEX

# mouse callback function

def draw_circle(event,x,y,flags,param):

if event == cv2.EVENT_LBUTTONDBLCLK:

i = 0

while True:

cv2.imshow('image',img) # to display the characters

k = cv2.waitKey(0)

cv2.putText(img, chr(k) , (x+i,y), font, 0.5, (0, 255, 0), 2, cv2.LINE_AA)

i+=10

# Press q to stop writing

if k == ord('q'):

break

# Create a black image, a window and bind the function to window

img = np.zeros((512,512,3), np.uint8)

cv2.namedWindow('image')

cv2.setMouseCallback('image',draw_circle)

while True:

cv2.imshow('image',img)

if cv2.waitKey(20) == 27:

break

cv2.destroyAllWindows()

In the above code, press ‘q’ to stop writing and left double click anywhere to again start writing.

You can play with mouse callback function using other mouse events. Hope you enjoy reading.

If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.

TheAILearner

Mastering Artificial Intelligence

Tag Archives: cv2.waitKey()

Creating a Bouncing Ball Screensaver using OpenCV-Python

Task:

Show current DateTime on live video using OpenCV-Python

Steps:

Code:

Write Text on images in real-time using OpenCV-Python

Steps:

Write Text on images at mouse click position using OpenCV-Python

Steps:

Code: