OpenCV: how to force the image window to appear on top of other windows?

Question

Using cvShowImage, one can easily show an image in OpenCV. However, how do you tell OpenCV to show the window on top of every other window?

I run a ful

Answer 1

I found the best solution posted in comments here: Python OpenCV open window on top of other applications

Simply add the command below after opening a window, e.g.

cv2.namedWindow('img_file_name', cv2.WINDOW_NORMAL) # Creates a window
os.system('''/usr/bin/osascript -e 'tell app "Finder" to set frontmost of process "python" to true' ''') # To make window active

Use "python" in lower case. Using "Python", as I found in some answers, gave me an error:

21:62: execution error: Finder got an error: Can’t set process "Python" to true. (-10006))

At first I tried editing the windows_cocoa.mm file, as suggested above, but it doesn't exist in my computer. I am using a mac osx mojave, OpenCV 3.4.2.

Answer 2

I found that all I needed to do was set my main window to fullscreen then back to normal. I did not need to open a separate window. I did not need to display a dummy image. I did not need to call waitKey.

    #!/usr/bin/env python
    import cv2
    import numpy

    WindowName="Main View"
    view_window = cv2.namedWindow(WindowName,cv2.WINDOW_NORMAL)

    # These two lines will force your "Main View" window to be on top with focus.
    cv2.setWindowProperty(WindowName,cv2.WND_PROP_FULLSCREEN,cv2.WINDOW_FULLSCREEN)
    cv2.setWindowProperty(WindowName,cv2.WND_PROP_FULLSCREEN,cv2.WINDOW_NORMAL)

    # The rest of this does not matter. This would be the rest of your program.
    # This just shows an image so that you can see that this example works.
    img = numpy.zeros((400,400,3), numpy.uint8)
    for x in range(0,401,100):
        for y in range(0,401,100):
            cv2.line(img,(x,0),(0,y),(128,128,254),1)
            cv2.line(img,(x,399),(0,y),(254,128,128),1)
            cv2.line(img,(399,y),(x,399),(128,254,128),1)
            cv2.line(img,(399,y),(x,0),(254,254,254),1)
    cv2.imshow(WindowName, img)
    cv2.waitKey(0)
    cv2.destroyWindow(WindowName)

Answer 3

import os os.system('''/usr/bin/osascript -e 'tell app "Finder" to set frontmost of process "Python" to true' ''')

Adding this before any of my code worked for me. Python 3.6.6 & macOS Mojave 10.14.2

Be careful though, the image is gonna pop up on one of your "Desktops" and not in any Maximized Window App screen (when you press the green button in the top left of your app)

Answer 4

OK, I figured it out which works for both OSX and Windows. You just need to create a full-screen window and show it for a very short time, then your next window from OpenCV will be in front. So, first to open a full-screen window:

cv::namedWindow("GetFocus", CV_WINDOW_NORMAL);
cv::Mat img = cv::Mat::zeros(100, 100, CV_8UC3);
cv::imshow("GetFocus", img);
cv::setWindowProperty("GetFocus", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
waitKey(1);
cv::setWindowProperty("GetFocus", CV_WND_PROP_FULLSCREEN, CV_WINDOW_NORMAL);
destroyWindow("GetFocus");

And then you can open up anther window that actually show the image:

Mat your_image = ...;
cv::namedWindow("ShowImg");
cv::imshow("ShowImg", your_image);

It works for me.

Answer 5

On MAC-OSX (El Capitan) OpenCV 3.1.0, calling moveWindow seems to bring the window just moved to the top.

Answer 6

My solution for OSX was to modify my OpenCV code (version 2.4.8), specifically the file windows_cocoa.mm in the highgui/src directory.

If you want to just bring the new window to the front without making it active, add the following line just before the end of the function cvNamedWindow() in windows_cocoa.mm:

[window orderFrontRegardless];

To force the new window to always be made active, add the following line instead:

[application activateIgnoringOtherApps:YES];

It's probably not the best idea for all windows but works in my situation. I got tired of always having to bring them to the front by clicking on them to make them active.