zoom_in_with_trackbar.py

import cv2

maxScaleUp = 100
scaleFactor = 1
scaleType = 0
maxType = 1

windowName = "Resize Image"
trackbarValue = "Scale"

# load an image
im = cv2.imread("/home/jean/Pictures/download.jpeg")

# Create a window to display results
cv2.namedWindow(windowName, cv2.WINDOW_AUTOSIZE)



# Callback functions
def scaleImage(*args):
    global scaleFactor
    global scaleType
    
    # Get the scale factor from the trackbar 
    scaleFactor = 1+ args[0]/100.0
    
    # Perform check if scaleFactor is zero
    if scaleFactor == 0:
        scaleFactor = 1
    
    # Resize the image
    scaledImage = cv2.resize(im, None, fx=scaleFactor,\
            fy = scaleFactor, interpolation = cv2.INTER_LINEAR)
    cv2.imshow(windowName, scaledImage)

# Callback functions
def scaleTypeImage(*args):
    global scaleType
    global scaleFactor
    scaleType = args[0]
    scaleFactor = 1 + scaleFactor/100.0
    if scaleFactor ==0:
        scaleFactor = 1
    scaledImage = cv2.resize(im, None, fx=scaleFactor,\
            fy = scaleFactor, interpolation = cv2.INTER_LINEAR)
    cv2.imshow(windowName, scaledImage)


cv2.createTrackbar(trackbarValue, windowName, scaleFactor, maxScaleUp, scaleImage)

cv2.imshow(windowName, im)
c = cv2.waitKey(0)

cv2.destroyAllWindows()