Python and OpenCV - is there any way of making sure sliding at the trackbar of cv2.createTrackbar will give me an odd value? -

let have code:

cv2.createtrackbar('kernal', 'window', 3, 21, callback) 

for time being, write code underneath check weather value got correspond cv2.gettrackbarpos odd or even, , if even, add 1 it. there other way using callback? because irritating part way slider not represent value getting (it 1 value lower if set number).