This document provides instructions for installing OpenCV 2.4.x with Qt on Windows, Linux, and Mac OS X. The steps are: 1. Install Qt SDK from the Qt website. 2. Download and unpack OpenCV 2.4.x from the OpenCV website. 3. Run CMake to configure and generate Makefile projects for OpenCV. Specify debug/release build configurations and enable Qt support. 4. Build and install OpenCV by running Make or mingw32-make, and add OpenCV libraries to the system path for use with Qt projects.

1. Installing OpenCV
2.4.x 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 guides
 Currently, only for Linux and Windows
 http://docs.opencv.org/doc/tutorials/introduction/table_of_c
ontent_introduction/table_of_content_introduction.html
 Prerequisites:
 [Mac OS X] Xcode with command line tools installed
 [Linux] GCC 4.4 or later
 N.B. This tutorial has been tested with OpenCV
2.3.1, 2.4.2, and 2.4.3 under Windows 7 and Mac
OS X 10.7+
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Installation

3. 1. Qt SDK (I)
 Download and install Qt SDK from http://qt-
project.org/downloads, using the offline installer
(current SDK release 1.2.1)
 [Windows-only] Perform a custom installation,
installing all the MinGW stuff. Components about
Harmattan, 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 2.4.x
 Download and unpack OpenCV 2.4.x from
http://opencv.org/
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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 two new folders named “cmake-debug” and
“cmake-release” inside the opencv folder
 Create a folder named “build_with_Qt” (or similar)
wherever you want
 create two new folders named “debug” and “release” inside
the “build_with_Qt” folder
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9. 3. Cmake (II)
 Create two new folders named “cmake-debug” and
“cmake-release” inside the opencv folder
 Create a folder named “build_with_Qt” (or similar)
wherever you want
It is not strongly mandatory… it
 create two new folders named “debug” and “release” inside
is only a “best practice”!
the “build_with_Qt” folder
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10. 3. Cmake (IV)
 Run Cmake
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11. 3. Cmake (V)
 “Where is the source code” field requires the
location of the opencv folder
 “Where to build the binaries” field requires the
location of the “cmake-debug” folder, previously
created
 Now press the button “Configure”…
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12. 3. Cmake (VI)
 In the next window, select “MingGW Makefiles”
under Windows, “Unix Makefiles” otherwise
 Then, press “Finish”
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13. 3. Cmake (VII)
 The Cmake window should appear in this way:
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14. 3. Cmake (VIII)
 Open the CMAKE entry
 assign the value Debug to the CMAKE_BUILD_TYPE
variable
 change the CMAKE_INSTALL_PREFIX to match the
“build_with_Qt/debug” folder
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15. 3. Cmake (IX)
 Open the WITH entry:
 check WITH_QT
 uncheck useless values (CUDA, CUFFT, EIGEN, and PVAPI, typically)
 Press “Configure”, again
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16. 3. Cmake (X)
 Open the Ungrupped Entries (or QT) with a red
background and add the location of qmake to the
variable QT_QMAKE_EXECUTABLE
 [Windows] qmake is in /Desktop/Qt/4.8.1/mingw/bin inside
the folder where Qt SDK has been installed
 [Linux/Mac] qmake is in /Desktop/Qt/4.8.1/gcc/bin inside
the folder where Qt SDK has been installed
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17. 3. Cmake (XI)
 Click again on “Configure” (until the entries
background becomes totally white)
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18. 3. Cmake (XII)
 Press “Generate”
 Repeat the steps reported on slides 11 - 18,
changing:
 the build destination folder from “cmake-debug” to “cmake-
release”
 the value of the CMAKE_BUILD_TYPE variable (in the
CMAKE entry) to Release
 the value of the CMAKE_INSTALL_PREFIX variable (in the
CMAKE entry) to match the “build_with_Qt/release” folder
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19. 4a. Final steps, on Linux/Mac
(I)
 Open the terminal, move to the “cmake-debug”
folder, type “make -jN”, where N is the number of
threads to use, and press enter
 Wait…
 Type “make install” to complete the OpenCV
installation
 Repeat the previous three steps for the “cmake-
release” folder
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20. 4a. Final steps, on Linux/Mac
(II)
 Add the following folders:
 /build_with_Qt/debug/bin
 /build_with_Qt/release/bin
to the DYLD_LIBRARY_PATH (Mac) or
LD_LIBRARY_PATH (Linux) environment variable.
You can perform this operation right inside QtCreator (“Build
Environments” field inside the Projects” tab).
 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 “cmake-debug”
folder, type “mingw32-make –j N”, where N is the
number of threads to use, and press enter
 Wait…
 Type “mingw32-make install” and press enter
 Repeat the previous three steps for the “cmake-release”
folder
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22. 4b. Final steps, on Windows
(II)
 Add to the PATH environment variable the following
folders:
 /build_with_Qt/debug/bin
 /build_with_Qt/release/bin
 QtSDK/Desktop/Qt/4.8.1/mingw/bin
 How do I set the PATH
variable? Read here.
 You can also perform this
operation inside QtCreator (“Build
Environments” field inside the
Projects” tab).
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23. 4b. Final steps, on Windows
(III)
 Copy the file “opencv.hpp” from “/include/opencv2”
to “include” (in your “build_with_Qt” folder)
 Done: you can start to use OpenCV with Qt!
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