getTrackbarPosBrightness

getTrackbarPos is a function in OpenCV’s HighGUI module that retrieves the current position of a trackbar created with createTrackbar in a specified window. It returns the trackbar’s value as an integer, reflecting its position within the trackbar’s defined range. The function is commonly used to query user-adjusted parameters in real time during image or video processing.

Signature and availability

In C++: int getTrackbarPos(const string& trackbarname, const string& winname);

In C: int getTrackbarPos(const char trackbarname, const char winname);

Both versions require that the trackbar exists in the given window. If the specified trackbar or window does not exist, the function’s behavior is undefined and may yield an unexpected value.

Usage context

getTrackbarPos is typically called inside a processing loop to read the current value of a trackbar and apply it to processing parameters (for example, adjusting brightness, threshold levels, or filter strength). It complements setTrackbarPos and createTrackbar, enabling a bidirectional interaction between the user interface and the algorithm.

Relation to other functions

The function is part of a small set of trackbar utilities in HighGUI. createTrackbar initializes a trackbar and connects it to a window, setTrackbarPos can adjust its value programmatically, and getTrackbarPos reads the current value, allowing dynamic parameter control.

Limitations

This function requires a GUI-capable OpenCV build and a running environment with display support. It is not applicable in headless or non-GUI backends.