An OpenCV utility function for displaying a set of easily-configurable trackbars and providing their results to an arbitrary callback - useful for quick prototyping and testing

call-with-trackbars.py

#Usage: `python call-with-trackbars.py example.jpg`

import sys
import cv2


#### Example usage ####
def edge_detect(p):
    edged = cv2.Canny(p["img"], p["low"] * 15, p["high"] * 15, apertureSize = (p["aperture"] * 2) + 3)
    cv2.imshow("Edged", edged)
    return edged


def main():
    path = str(sys.argv[1])
    
    img = cv2.imread(path, cv2.COLOR_BGR2GRAY)
    
    variables = [
        {
            "name": "low",
            "default": 0,
            "max": 100
        },
        {
            "name": "high",
            "default": 0,
            "max": 100
        },
        {
            "name": "aperture",
            "default": 0,
            "max": 2
        },
    ]
    
    call_with_trackbars({ "img": img }, variables, edge_detect)


#### Utility functions ####

#Create trackbars (sliders) for `variables` in a window named "Variables". When the trackbars change value, provide those `values`, merged with the provided `parameters`, to `callback`.
def call_with_trackbars(parameters, variables, callback):
    cv2.namedWindow("Variables", cv2.WINDOW_NORMAL)
    
    for variable in variables:
        cv2.createTrackbar(variable["name"], "Variables", variable["default"], variable["max"], nothing)
    
    cv2.resizeWindow("Variables", 500, 200)
    cv2.moveWindow("Variables", 0, 500) #Doesn't work on macOS at the moment due to a bug in OpenCV (https://github.com/opencv/opencv/issues/16343)
    
    values = {}
    last_values = None
    while(1):
        #Break when the "Escape" key is pressed.
        k = cv2.waitKey(1) & 0xFF
        if k == 27:
            break
        
        for variable in variables:
            values[variable["name"]] = cv2.getTrackbarPos(variable["name"], "Variables")

        if(values == last_values):
            continue
        last_values = values.copy()
        
        print(values)
        callback({**parameters, **values})


def nothing(x):
  pass


main()

Released under the MIT license. Please let me know if you find this useful!

Screenshot of usage: