RGB Trackbar in OpenCV python
Trackbars are helpful to instantaneously test and experiment with different parameters and values and observe the output in real time which out re-running the program again and again.
Read tutorial on How to add trackbar in your application.
Computer graphics are made of pixels [Read more on Anatomy of a digital image.]
Any color you seen on your screen has 3 component Red, green and blue.
The value of Red, Green and Blue can range from 0 -255 and by mixing different values of red, green and blue a new color is formed.
To Visualize this Mixing of R,G,B values we can create a python script.
The below python script contains 3 trackbars to control the concentration of Red, Green, and Blue color in the image.
- R – Red
- G – Green
- B – Blue
Each trackbas has fixed lower bound of 0 and upper bound of 255.
RGB Trackbar python code
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#import opencv and numpy import cv2 import numpy as np #trackbar callback fucntion does nothing but required for trackbar def nothing(x): pass #create a seperate window named 'controls' for trackbar cv2.namedWindow('controls',2) cv2.resizeWindow("controls", 550,10); #create trackbar in 'controls' window with name 'r'' cv2.createTrackbar('r','controls',0,255,nothing) cv2.createTrackbar('g','controls',0,255,nothing) cv2.createTrackbar('b','controls',0,255,nothing) while(1): #create a black image img = np.zeros((512,512,3), np.uint8) #returns current position/value of trackbar r= int(cv2.getTrackbarPos('r','controls')) g=int(cv2.getTrackbarPos('g','controls')) b=int(cv2.getTrackbarPos('b','controls')) #assign trackbar value to r,g,b channel of the image img[:,:,0]=b img[:,:,1]=g img[:,:,2]=r cv2.imshow('img',img) #waitfor the user to press escape and break the while loop k = cv2.waitKey(1) & 0xFF if k == 27: break #destroys all window cv2.destroyAllWindows() |
By sliding the trackbar you can change the value of Red, Green, and Blue components and observe how the color in the explore window changes.
More Trackbar Example:
- HSV color trackbar
- Image blur trackbar
- Brightness, and Contrast trackbar.
