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Please see the latest blog to install Open CV 3 on mac OS here !

Notes : Consider following suggestions before you start installing Open CV on your Mac 1.

Using Macports to install Open CV – it’s easier and perfect 4. Extract the folder and keep the Open CV folder at some better place in your mac (Not in downloads) note: there’s a space between two dots.

For convenience we have used the filename as the window name.

This is nice because Open CV automatically puts the window name at the top of the window, so we can tell which file we are viewing (see Figure 4-1). tries to start a thread that updates the window automatically and handles resizing and so forth.

If the user // presses the left button, we start a box.

// when the user releases that button, then we // add the box to the current image.

A return value of indicates that no thread could be started—for example, because there is no support for this feature in the version of Open CV that you are using.

Note that, if you do not start a separate window thread, Open CV can react to user interface actions only when it is explicitly given time to do so (this happens when your program invokes we tell Open CV to wait 100 ms for a key stroke.

This means that, to enable response to mouse clicks, we must first write a callback routine that Open CV can call whenever a mouse event occurs.

Once we have done that, we must register the callback with Open CV, thereby informing Open CV that this is the correct function to use whenever the user does something with the mouse over a particular window. For those of you who are a little rusty on your event-driven program lingo, the can be any function that takes the correct set of arguments and returns the correct type.

The first argument here is the name of the window within which we intend to draw. Let's now put together a simple program that will display an image on the screen.

We can read a filename from the command line, create a window, and put our image in the window in 25 lines, including comments and tidily cleaning up our memory allocations!

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