Tutorial for installing OpenCV 2.3.1 with Qt. Slides made for the Computer Vision course at Politecnico di Torino (academic year 2011/2012).

1. Installing OpenCV
2.3.1 with Qt
Luigi De Russis
Politecnico di Torino
Dipartimento di Automatica e Informatica (DAUIN)
Torino - Italy
luigi.derussis@polito.it
This work is licensed under the Creative Commons (CC BY-SA)
License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-sa/3.0/

2. 0. Getting started…
 Official installation guide:
http://opencv.willowgarage.com/wiki/InstallGuide
 Prerequisites:
 [Mac OS X] Xcode 3.2 or later
 [Linux] GCC 4.3 or later
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3. 1. Qt SDK (I)
 Download and install Qt SDK from
http://qt.nokia.com/downloads, using the offline
installer (current release 4.7.4)
 [Windows-only] Perform a custom installation,
installing all the mingw32 stuff. Components about
Meego, Symbian, etc. are not necessary for our
purpose (see next slide)
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4. 1. Qt SDK (II) - Windows
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5. 1. Qt SDK (II) - Windows
At the end, check if the folder
C:QtSDKmingwbin (or similar)
is included in the PATH variable
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6. 2. OpenCV 2.3.1
 Download and unpack OpenCV 2.3.1 from
http://opencv.willowgarage.com/wiki
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7. 3. Cmake (I)
 Download and install Cmake from
http://www.cmake.org/
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8. 3. Cmake (II)
 Create a folder named “builds_with_Qt” (or similar)
wherever you want (suggested location: inside the
opencv folder)
 Create two new folders named “debug” and
“release” inside the “builds_with_Qt” folder
 [Mac-only] Warning: choose carefully where you put
the “builds_with_Qt” folder. To move the folder, thus
maintaining the compiled opencv library working,
may require a little bit effort (by using
“install_name_tool”).
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9. 3. Cmake (II)
 Create a folder named “builds_with_Qt” (or similar)
wherever you want (suggested location: inside the
opencv folder)
 Create two new folders named “debug” and
It is not strongly mandatory…
“release” inside the “builds_with_Qt” folder
only a “best practice”!
 [Mac-only] Warning: choose carefully where you put
the “builds_with_Qt” folder. To move the folder, thus
maintaining the compiled opencv library working,
may require a little bit effort (by using
“install_name_tool”).
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10. 3. Cmake (III)
 Run Cmake
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11. 3. Cmake (III)
 “Where is the source code” field requires the
location of the opencv folder
 “Where to build the binaries” field requires the
location of the “debug” folder, previously created
 Now press the button “Configure”…
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12. 3. Cmake (IV)
 In the next window, select “MingGW Makefiles”
under Windows, “Unix Makefiles” otherwise
 Then, press “Finish”
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13. 3. Cmake (V)
 The Cmake window should appear in this way:
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14. 3. Cmake (VI)
 Open the CMAKE entry and assign the value
DEBUG to the CMAKE_BUILD_TYPE variable
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15. 3. Cmake (VII)
 Open the WITH entry:
 uncheck WITH_CUDA and WITH_EIGEN
 check WITH_QT
 Press “Configure”, again
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16. 3. Cmake (VIII)
 Open the QT entry with a red background and add
the location of qmake to the variable
QT_QMAKE_EXECUTABLE (qmake is in
/Desktop/Qt/4.7.4/mingw/bin inside the folder where
Qt SDK has been installed)
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17. 3. Cmake (IX)
 Click again on “Configure” (until the entries
background becomes totally white)
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18. 3. Cmake (X)
 Press “Generate”
 Repeat the steps reported on slides 11 - 18,
changing:
 the build destination folder from “debug” to “release”
 the value of the CMAKE_BUILD_TYPE variable (in
the CMAKE entry) to RELEASE
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19. 4a. Final steps, on Linux/Mac
(I)
 Open the terminal, move to the “debug” folder, type
“make -jN”, where N is the number of threads to use
(typically, dual core processor can efficiently handle
4 threads), and press enter
 Wait…
 Repeat the previous two steps for the “release”
folder
 Copy the “include” folder (the one inside the “build”
folder) from the WINDOWS version of opencv in
your “builds_with_Qt” folder
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20. 4a. Final steps, on Linux/Mac
(II)
 Copy the file “opencv.hpp” from “/include/opencv2”
to “include” (in your “builds_with_Qt” folder)
 Done: you can start to use OpenCV with Qt!
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21. 4b. Final steps, on Windows (I)
 Open the command prompt, move to the “debug” folder,
type “mingw32-make” and press enter
 Wait…
 Repeat the previous two steps for the “release” folder
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22. 4b. Final steps, on Windows
(II)
 Add to the PATH environment variable the location
of the following folders:
 bin folder inside “debug”
 bin folder inside “release”
 QtSDK/Desktop/Qt/4.7.4/mingw/bin
 How do I set the
PATH variable?
Read here.
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23. 4b. Final steps, on Windows
(III)
 Copy the “include” folder (the one inside the “build”
folder in the opencv folder) in your “builds_with_Qt”
folder
 Copy the file “opencv.hpp” from “/include/opencv2”
to “include” (in your “builds_with_Qt” folder)
 Done: you can start to use OpenCV with Qt!
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