2.5 KiB
Thresholding Operations using inRange
Goal
In this tutorial you will learn how to:
- Perform basic thresholding operations using OpenCV function @ref cv::inRange
- Detect an object based on the range of pixel values it has
Theory
- In the previous tutorial, we learnt how perform thresholding using @ref cv::threshold function.
- In this tutorial, we will learn how to do it using @ref cv::inRange function.
- The concept remains same, but now we add a range of pixel values we need.
Code
The tutorial code's is shown lines below. You can also download it from here @include samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp
Explanation
-# Let's check the general structure of the program: - Create two Matrix elements to store the frames @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp mat - Capture the video stream from default capturing device. @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp cap - Create a window to display the default frame and the threshold frame. @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp window - Create trackbars to set the range of RGB values @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp trackbar - Until the user want the program to exit do the following @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp while - Show the images @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp show - For a trackbar which controls the lower range, say for example Red value: @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp low - For a trackbar which controls the upper range, say for example Red value: @snippet samples/cpp/tutorial_code/ImgProc/Threshold_inRange.cpp high - It is necessary to find the maximum and minimum value to avoid discrepancies such as the high value of threshold becoming less the low value.
Results
-# After compiling this program, run it. The program will open two windows
-# As you set the RGB range values from the trackbar, the resulting frame will be visible in the other window.
