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