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OpenCVIntroduction

Lecture #3January 27, 2016

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… and so it begins

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… and today …© Bru ce A. Drap er & J. Ro ss Bev erid g e, Jan u ary 2 7 , 2 016

Need to Start Somewhere

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OpenCV : First Steps (C++)• Include OpenCV

• Most important classes:– Mat (image/matrix class)– VideoCapture (video class)– Windows (not really a class)

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Read/Show Example (from OpenCV)

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Simple Image Access (from OpenCV)

• 1st image type: CV_8UC1• 2nd image type: CV_8UC3• Unfortunately, Mat is not templated

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VideoCapture Example

• First part of code opens a video stream• 2nd part gets properties from stream• Note that this will read many (but not all)

video formats

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VideoCapture Example II

• Grab() advances stream• Retrieve() gets the current frame• pyrDown() reduces image size by 1/2

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Accessing Color Images

• median_img is a 3 color byte image– Passed in as argument, not shown

• mad_img is a 1 color floating point image– Inidcated by CV_32FC1

• Notice Mat is not typed, but iterators are– So is the single pixel accessor

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Accessing Images (continued)

• Iterators accessed as you expect

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Useful Functions for this Assignment

• getRotationMatrix2D• getAffineTransform• getPerspectiveTransform• invertAffineTransform• warpAffine• warpPerspective

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New projectin Eclipse

I am going to follow the KISS process here(which actually makes some things hard).

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Here is what you get …

Notice the lack of anything relate to OpenCV

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Customize Project Properties

Essentially, we are telling Eclipse to stop trying to be helpful.

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IncludesBe careful you have GNU C++ selected.Obviously these are my paths on my Yosemite installed Mac.

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LibrariesSince we are building our own extremely simple Makefile, not clear this step is needed.

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Now, we need a source file

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Now, make meets KISS• Why am I being so primitive?

– Walk before you run …– Be able to test from a command line prompt!

• As your systems grow, so too will the automation in your Makefile.

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Eclipse and compiling = targetsNote new targets are created in the targets window in the upper right.

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Gotcha!

Remove“Debug”

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Run