OpenCV  3.3.0-dev
Open Source Computer Vision
Modules | Typedefs | Enumerations | Functions
High-level GUI

Modules

 OpenGL support
 
 Qt New Functions
 
 WinRT support
 
 C API
 

Typedefs

typedef void(* cv::ButtonCallback) (int state, void *userdata)
 Callback function for a button created by cv::createButton. More...
 
typedef void(* cv::MouseCallback) (int event, int x, int y, int flags, void *userdata)
 Callback function for mouse events. see cv::setMouseCallback. More...
 
typedef void(* cv::OpenGlDrawCallback) (void *userdata)
 Callback function defined to be called every frame. See cv::setOpenGlDrawCallback. More...
 
typedef void(* cv::TrackbarCallback) (int pos, void *userdata)
 Callback function for Trackbar see cv::createTrackbar. More...
 

Enumerations

enum  cv::MouseEventFlags {
  cv::EVENT_FLAG_LBUTTON = 1,
  cv::EVENT_FLAG_RBUTTON = 2,
  cv::EVENT_FLAG_MBUTTON = 4,
  cv::EVENT_FLAG_CTRLKEY = 8,
  cv::EVENT_FLAG_SHIFTKEY = 16,
  cv::EVENT_FLAG_ALTKEY = 32
}
 Mouse Event Flags see cv::MouseCallback. More...
 
enum  cv::MouseEventTypes {
  cv::EVENT_MOUSEMOVE = 0,
  cv::EVENT_LBUTTONDOWN = 1,
  cv::EVENT_RBUTTONDOWN = 2,
  cv::EVENT_MBUTTONDOWN = 3,
  cv::EVENT_LBUTTONUP = 4,
  cv::EVENT_RBUTTONUP = 5,
  cv::EVENT_MBUTTONUP = 6,
  cv::EVENT_LBUTTONDBLCLK = 7,
  cv::EVENT_RBUTTONDBLCLK = 8,
  cv::EVENT_MBUTTONDBLCLK = 9,
  cv::EVENT_MOUSEWHEEL = 10,
  cv::EVENT_MOUSEHWHEEL = 11
}
 Mouse Events see cv::MouseCallback. More...
 
enum  cv::QtButtonTypes {
  cv::QT_PUSH_BUTTON = 0,
  cv::QT_CHECKBOX = 1,
  cv::QT_RADIOBOX = 2,
  cv::QT_NEW_BUTTONBAR = 1024
}
 Qt "button" type. More...
 
enum  cv::QtFontStyles {
  cv::QT_STYLE_NORMAL = 0,
  cv::QT_STYLE_ITALIC = 1,
  cv::QT_STYLE_OBLIQUE = 2
}
 Qt font style. More...
 
enum  cv::QtFontWeights {
  cv::QT_FONT_LIGHT = 25,
  cv::QT_FONT_NORMAL = 50,
  cv::QT_FONT_DEMIBOLD = 63,
  cv::QT_FONT_BOLD = 75,
  cv::QT_FONT_BLACK = 87
}
 Qt font weight. More...
 
enum  cv::WindowFlags {
  cv::WINDOW_NORMAL = 0x00000000,
  cv::WINDOW_AUTOSIZE = 0x00000001,
  cv::WINDOW_OPENGL = 0x00001000,
  cv::WINDOW_FULLSCREEN = 1,
  cv::WINDOW_FREERATIO = 0x00000100,
  cv::WINDOW_KEEPRATIO = 0x00000000,
  cv::WINDOW_GUI_EXPANDED =0x00000000,
  cv::WINDOW_GUI_NORMAL = 0x00000010
}
 Flags for cv::namedWindow. More...
 
enum  cv::WindowPropertyFlags {
  cv::WND_PROP_FULLSCREEN = 0,
  cv::WND_PROP_AUTOSIZE = 1,
  cv::WND_PROP_ASPECT_RATIO = 2,
  cv::WND_PROP_OPENGL = 3,
  cv::WND_PROP_VISIBLE = 4
}
 Flags for cv::setWindowProperty / cv::getWindowProperty. More...
 

Functions

int cv::createTrackbar (const String &trackbarname, const String &winname, int *value, int count, TrackbarCallback onChange=0, void *userdata=0)
 Creates a trackbar and attaches it to the specified window. More...
 
void cv::destroyAllWindows ()
 Destroys all of the HighGUI windows. More...
 
void cv::destroyWindow (const String &winname)
 Destroys the specified window. More...
 
int cv::getMouseWheelDelta (int flags)
 Gets the mouse-wheel motion delta, when handling mouse-wheel events cv::EVENT_MOUSEWHEEL and cv::EVENT_MOUSEHWHEEL. More...
 
int cv::getTrackbarPos (const String &trackbarname, const String &winname)
 Returns the trackbar position. More...
 
double cv::getWindowProperty (const String &winname, int prop_id)
 Provides parameters of a window. More...
 
void cv::imshow (const String &winname, InputArray mat)
 Displays an image in the specified window. More...
 
void cv::moveWindow (const String &winname, int x, int y)
 Moves window to the specified position. More...
 
void cv::namedWindow (const String &winname, int flags=WINDOW_AUTOSIZE)
 Creates a window. More...
 
void cv::resizeWindow (const String &winname, int width, int height)
 Resizes window to the specified size. More...
 
void cv::resizeWindow (const String &winname, const cv::Size &size)
 
Rect cv::selectROI (const String &windowName, InputArray img, bool showCrosshair=true, bool fromCenter=false)
 Selects ROI on the given image. Function creates a window and allows user to select a ROI using mouse. Controls: use space or enter to finish selection, use key c to cancel selection (function will return the zero cv::Rect). More...
 
Rect cv::selectROI (InputArray img, bool showCrosshair=true, bool fromCenter=false)
 
void cv::selectROIs (const String &windowName, InputArray img, std::vector< Rect > &boundingBoxes, bool showCrosshair=true, bool fromCenter=false)
 Selects ROIs on the given image. Function creates a window and allows user to select a ROIs using mouse. Controls: use space or enter to finish current selection and start a new one, use esc to terminate multiple ROI selection process. More...
 
void cv::setMouseCallback (const String &winname, MouseCallback onMouse, void *userdata=0)
 Sets mouse handler for the specified window. More...
 
void cv::setTrackbarMax (const String &trackbarname, const String &winname, int maxval)
 Sets the trackbar maximum position. More...
 
void cv::setTrackbarMin (const String &trackbarname, const String &winname, int minval)
 Sets the trackbar minimum position. More...
 
void cv::setTrackbarPos (const String &trackbarname, const String &winname, int pos)
 Sets the trackbar position. More...
 
void cv::setWindowProperty (const String &winname, int prop_id, double prop_value)
 Changes parameters of a window dynamically. More...
 
void cv::setWindowTitle (const String &winname, const String &title)
 Updates window title. More...
 
int cv::startWindowThread ()
 
int cv::waitKey (int delay=0)
 Waits for a pressed key. More...
 
int cv::waitKeyEx (int delay=0)
 Similar to waitKey, but returns full key code. More...
 

Detailed Description

While OpenCV was designed for use in full-scale applications and can be used within functionally rich UI frameworks (such as Qt*, WinForms*, or Cocoa*) or without any UI at all, sometimes there it is required to try functionality quickly and visualize the results. This is what the HighGUI module has been designed for.

It provides easy interface to:

Typedef Documentation

§ ButtonCallback

typedef void(* cv::ButtonCallback) (int state, void *userdata)

Callback function for a button created by cv::createButton.

Parameters
statecurrent state of the button. It could be -1 for a push button, 0 or 1 for a check/radio box button.
userdataThe optional parameter.

§ MouseCallback

typedef void(* cv::MouseCallback) (int event, int x, int y, int flags, void *userdata)

Callback function for mouse events. see cv::setMouseCallback.

Parameters
eventone of the cv::MouseEventTypes constants.
xThe x-coordinate of the mouse event.
yThe y-coordinate of the mouse event.
flagsone of the cv::MouseEventFlags constants.
userdataThe optional parameter.

§ OpenGlDrawCallback

typedef void(* cv::OpenGlDrawCallback) (void *userdata)

Callback function defined to be called every frame. See cv::setOpenGlDrawCallback.

Parameters
userdataThe optional parameter.

§ TrackbarCallback

typedef void(* cv::TrackbarCallback) (int pos, void *userdata)

Callback function for Trackbar see cv::createTrackbar.

Parameters
poscurrent position of the specified trackbar.
userdataThe optional parameter.

Enumeration Type Documentation

§ MouseEventFlags

Mouse Event Flags see cv::MouseCallback.

Enumerator
EVENT_FLAG_LBUTTON 

indicates that the left mouse button is down.

EVENT_FLAG_RBUTTON 

indicates that the right mouse button is down.

EVENT_FLAG_MBUTTON 

indicates that the middle mouse button is down.

EVENT_FLAG_CTRLKEY 

indicates that CTRL Key is pressed.

EVENT_FLAG_SHIFTKEY 

indicates that SHIFT Key is pressed.

EVENT_FLAG_ALTKEY 

indicates that ALT Key is pressed.

§ MouseEventTypes

Mouse Events see cv::MouseCallback.

Enumerator
EVENT_MOUSEMOVE 

indicates that the mouse pointer has moved over the window.

EVENT_LBUTTONDOWN 

indicates that the left mouse button is pressed.

EVENT_RBUTTONDOWN 

indicates that the right mouse button is pressed.

EVENT_MBUTTONDOWN 

indicates that the middle mouse button is pressed.

EVENT_LBUTTONUP 

indicates that left mouse button is released.

EVENT_RBUTTONUP 

indicates that right mouse button is released.

EVENT_MBUTTONUP 

indicates that middle mouse button is released.

EVENT_LBUTTONDBLCLK 

indicates that left mouse button is double clicked.

EVENT_RBUTTONDBLCLK 

indicates that right mouse button is double clicked.

EVENT_MBUTTONDBLCLK 

indicates that middle mouse button is double clicked.

EVENT_MOUSEWHEEL 

positive and negative values mean forward and backward scrolling, respectively.

EVENT_MOUSEHWHEEL 

positive and negative values mean right and left scrolling, respectively.

§ QtButtonTypes

Qt "button" type.

Enumerator
QT_PUSH_BUTTON 

Push button.

QT_CHECKBOX 

Checkbox button.

QT_RADIOBOX 

Radiobox button.

QT_NEW_BUTTONBAR 

Button should create a new buttonbar.

§ QtFontStyles

Qt font style.

Enumerator
QT_STYLE_NORMAL 

Normal font.

QT_STYLE_ITALIC 

Italic font.

QT_STYLE_OBLIQUE 

Oblique font.

§ QtFontWeights

Qt font weight.

Enumerator
QT_FONT_LIGHT 

Weight of 25.

QT_FONT_NORMAL 

Weight of 50.

QT_FONT_DEMIBOLD 

Weight of 63.

QT_FONT_BOLD 

Weight of 75.

QT_FONT_BLACK 

Weight of 87.

§ WindowFlags

Flags for cv::namedWindow.

Enumerator
WINDOW_NORMAL 

the user can resize the window (no constraint) / also use to switch a fullscreen window to a normal size.

WINDOW_AUTOSIZE 

the user cannot resize the window, the size is constrainted by the image displayed.

WINDOW_OPENGL 

window with opengl support.

WINDOW_FULLSCREEN 

change the window to fullscreen.

WINDOW_FREERATIO 

the image expends as much as it can (no ratio constraint).

WINDOW_KEEPRATIO 

the ratio of the image is respected.

WINDOW_GUI_EXPANDED 

status bar and tool bar

WINDOW_GUI_NORMAL 

old fashious way

§ WindowPropertyFlags

Flags for cv::setWindowProperty / cv::getWindowProperty.

Enumerator
WND_PROP_FULLSCREEN 

fullscreen property (can be WINDOW_NORMAL or WINDOW_FULLSCREEN).

WND_PROP_AUTOSIZE 

autosize property (can be WINDOW_NORMAL or WINDOW_AUTOSIZE).

WND_PROP_ASPECT_RATIO 

window's aspect ration (can be set to WINDOW_FREERATIO or WINDOW_KEEPRATIO).

WND_PROP_OPENGL 

opengl support.

WND_PROP_VISIBLE 

checks whether the window exists and is visible

Function Documentation

§ createTrackbar()

int cv::createTrackbar ( const String trackbarname,
const String winname,
int *  value,
int  count,
TrackbarCallback  onChange = 0,
void *  userdata = 0 
)

Creates a trackbar and attaches it to the specified window.

The function createTrackbar creates a trackbar (a slider or range control) with the specified name and range, assigns a variable value to be a position synchronized with the trackbar and specifies the callback function onChange to be called on the trackbar position change. The created trackbar is displayed in the specified window winname.

Note

[Qt Backend Only] winname can be empty (or NULL) if the trackbar should be attached to the control panel.

Clicking the label of each trackbar enables editing the trackbar values manually.

Parameters
trackbarnameName of the created trackbar.
winnameName of the window that will be used as a parent of the created trackbar.
valueOptional pointer to an integer variable whose value reflects the position of the slider. Upon creation, the slider position is defined by this variable.
countMaximal position of the slider. The minimal position is always 0.
onChangePointer to the function to be called every time the slider changes position. This function should be prototyped as void Foo(int,void*); , where the first parameter is the trackbar position and the second parameter is the user data (see the next parameter). If the callback is the NULL pointer, no callbacks are called, but only value is updated.
userdataUser data that is passed as is to the callback. It can be used to handle trackbar events without using global variables.
Examples:
AddingImagesTrackbar.cpp, camshiftdemo.cpp, contours2.cpp, demhist.cpp, distrans.cpp, edge.cpp, falsecolor.cpp, ffilldemo.cpp, fitellipse.cpp, laplace.cpp, MatchTemplate_Demo.cpp, morphology2.cpp, Morphology_1.cpp, and pca.cpp.

§ destroyAllWindows()

void cv::destroyAllWindows ( )

Destroys all of the HighGUI windows.

The function destroyAllWindows destroys all of the opened HighGUI windows.

§ destroyWindow()

void cv::destroyWindow ( const String winname)

Destroys the specified window.

The function destroyWindow destroys the window with the given name.

Parameters
winnameName of the window to be destroyed.
Examples:
camshiftdemo.cpp, ffilldemo.cpp, grabcut.cpp, and shape_example.cpp.

§ getMouseWheelDelta()

int cv::getMouseWheelDelta ( int  flags)

Gets the mouse-wheel motion delta, when handling mouse-wheel events cv::EVENT_MOUSEWHEEL and cv::EVENT_MOUSEHWHEEL.

For regular mice with a scroll-wheel, delta will be a multiple of 120. The value 120 corresponds to a one notch rotation of the wheel or the threshold for action to be taken and one such action should occur for each delta. Some high-precision mice with higher-resolution freely-rotating wheels may generate smaller values.

For cv::EVENT_MOUSEWHEEL positive and negative values mean forward and backward scrolling, respectively. For cv::EVENT_MOUSEHWHEEL, where available, positive and negative values mean right and left scrolling, respectively.

With the C API, the macro CV_GET_WHEEL_DELTA(flags) can be used alternatively.

Note

Mouse-wheel events are currently supported only on Windows.

Parameters
flagsThe mouse callback flags parameter.

§ getTrackbarPos()

int cv::getTrackbarPos ( const String trackbarname,
const String winname 
)

Returns the trackbar position.

The function returns the current position of the specified trackbar.

Note

[Qt Backend Only] winname can be empty (or NULL) if the trackbar is attached to the control panel.

Parameters
trackbarnameName of the trackbar.
winnameName of the window that is the parent of the trackbar.
Examples:
falsecolor.cpp.

§ getWindowProperty()

double cv::getWindowProperty ( const String winname,
int  prop_id 
)

Provides parameters of a window.

The function getWindowProperty returns properties of a window.

Parameters
winnameName of the window.
prop_idWindow property to retrieve. The following operation flags are available: (cv::WindowPropertyFlags)
See also
setWindowProperty

§ imshow()

void cv::imshow ( const String winname,
InputArray  mat 
)

Displays an image in the specified window.

The function imshow displays an image in the specified window. If the window was created with the cv::WINDOW_AUTOSIZE flag, the image is shown with its original size, however it is still limited by the screen resolution. Otherwise, the image is scaled to fit the window. The function may scale the image, depending on its depth:

  • If the image is 8-bit unsigned, it is displayed as is.
  • If the image is 16-bit unsigned or 32-bit integer, the pixels are divided by 256. That is, the value range [0,255*256] is mapped to [0,255].
  • If the image is 32-bit or 64-bit floating-point, the pixel values are multiplied by 255. That is, the value range [0,1] is mapped to [0,255].

If window was created with OpenGL support, cv::imshow also support ogl::Buffer , ogl::Texture2D and cuda::GpuMat as input.

If the window was not created before this function, it is assumed creating a window with cv::WINDOW_AUTOSIZE.

If you need to show an image that is bigger than the screen resolution, you will need to call namedWindow("", WINDOW_NORMAL) before the imshow.

Note
This function should be followed by cv::waitKey function which displays the image for specified milliseconds. Otherwise, it won't display the image. For example, waitKey(0) will display the window infinitely until any keypress (it is suitable for image display). waitKey(25) will display a frame for 25 ms, after which display will be automatically closed. (If you put it in a loop to read videos, it will display the video frame-by-frame)

[Windows Backend Only] Pressing Ctrl+C will copy the image to the clipboard.

[Windows Backend Only] Pressing Ctrl+S will show a dialog to save the image.

Parameters
winnameName of the window.
matImage to be shown.
Examples:
AddingImagesTrackbar.cpp, camshiftdemo.cpp, cloning_demo.cpp, contours2.cpp, convexhull.cpp, copyMakeBorder_demo.cpp, demhist.cpp, distrans.cpp, Drawing_1.cpp, Drawing_2.cpp, edge.cpp, facedetect.cpp, falsecolor.cpp, ffilldemo.cpp, fitellipse.cpp, fld_lines.cpp, grabcut.cpp, hog.cpp, houghcircles.cpp, houghlines.cpp, image_alignment.cpp, kalman.cpp, kmeans.cpp, laplace.cpp, lkdemo.cpp, lsd_lines.cpp, MatchTemplate_Demo.cpp, minarea.cpp, morphology2.cpp, Morphology_1.cpp, npr_demo.cpp, pca.cpp, peopledetect.cpp, polar_transforms.cpp, Pyramids.cpp, segment_objects.cpp, shape_example.cpp, Smoothing.cpp, Sobel_Demo.cpp, train_HOG.cpp, videowriter_basic.cpp, warpPerspective_demo.cpp, and watershed.cpp.

§ moveWindow()

void cv::moveWindow ( const String winname,
int  x,
int  y 
)

Moves window to the specified position.

Parameters
winnameName of the window.
xThe new x-coordinate of the window.
yThe new y-coordinate of the window.
Examples:
Drawing_1.cpp, image_alignment.cpp, Morphology_1.cpp, polar_transforms.cpp, shape_example.cpp, and warpPerspective_demo.cpp.

§ namedWindow()

void cv::namedWindow ( const String winname,
int  flags = WINDOW_AUTOSIZE 
)

Creates a window.

The function namedWindow creates a window that can be used as a placeholder for images and trackbars. Created windows are referred to by their names.

If a window with the same name already exists, the function does nothing.

You can call cv::destroyWindow or cv::destroyAllWindows to close the window and de-allocate any associated memory usage. For a simple program, you do not really have to call these functions because all the resources and windows of the application are closed automatically by the operating system upon exit.

Note

Qt backend supports additional flags:

  • WINDOW_NORMAL or WINDOW_AUTOSIZE: WINDOW_NORMAL enables you to resize the window, whereas WINDOW_AUTOSIZE adjusts automatically the window size to fit the displayed image (see imshow ), and you cannot change the window size manually.
  • WINDOW_FREERATIO or WINDOW_KEEPRATIO: WINDOW_FREERATIO adjusts the image with no respect to its ratio, whereas WINDOW_KEEPRATIO keeps the image ratio.
  • WINDOW_GUI_NORMAL or WINDOW_GUI_EXPANDED: WINDOW_GUI_NORMAL is the old way to draw the window without statusbar and toolbar, whereas WINDOW_GUI_EXPANDED is a new enhanced GUI. By default, flags == WINDOW_AUTOSIZE | WINDOW_KEEPRATIO | WINDOW_GUI_EXPANDED
Parameters
winnameName of the window in the window caption that may be used as a window identifier.
flagsFlags of the window. The supported flags are: (cv::WindowFlags)
Examples:
AddingImagesTrackbar.cpp, camshiftdemo.cpp, contours2.cpp, copyMakeBorder_demo.cpp, demhist.cpp, distrans.cpp, edge.cpp, falsecolor.cpp, ffilldemo.cpp, fitellipse.cpp, grabcut.cpp, image_alignment.cpp, laplace.cpp, lkdemo.cpp, MatchTemplate_Demo.cpp, morphology2.cpp, Morphology_1.cpp, pca.cpp, peopledetect.cpp, polar_transforms.cpp, segment_objects.cpp, Smoothing.cpp, train_HOG.cpp, warpPerspective_demo.cpp, and watershed.cpp.

§ resizeWindow() [1/2]

void cv::resizeWindow ( const String winname,
int  width,
int  height 
)

Resizes window to the specified size.

Note
  • The specified window size is for the image area. Toolbars are not counted.
  • Only windows created without cv::WINDOW_AUTOSIZE flag can be resized.
Parameters
winnameWindow name.
widthThe new window width.
heightThe new window height.

§ resizeWindow() [2/2]

void cv::resizeWindow ( const String winname,
const cv::Size size 
)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters
winnameWindow name.
sizeThe new window size.

§ selectROI() [1/2]

Rect cv::selectROI ( const String windowName,
InputArray  img,
bool  showCrosshair = true,
bool  fromCenter = false 
)

Selects ROI on the given image. Function creates a window and allows user to select a ROI using mouse. Controls: use space or enter to finish selection, use key c to cancel selection (function will return the zero cv::Rect).

Parameters
windowNamename of the window where selection process will be shown.
imgimage to select a ROI.
showCrosshairif true crosshair of selection rectangle will be shown.
fromCenterif true center of selection will match initial mouse position. In opposite case a corner of selection rectangle will correspont to the initial mouse position.
Returns
selected ROI or empty rect if selection canceled.
Note
The function sets it's own mouse callback for specified window using cv::setMouseCallback(windowName, ...). After finish of work an empty callback will be set for the used window.

§ selectROI() [2/2]

Rect cv::selectROI ( InputArray  img,
bool  showCrosshair = true,
bool  fromCenter = false 
)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

§ selectROIs()

void cv::selectROIs ( const String windowName,
InputArray  img,
std::vector< Rect > &  boundingBoxes,
bool  showCrosshair = true,
bool  fromCenter = false 
)

Selects ROIs on the given image. Function creates a window and allows user to select a ROIs using mouse. Controls: use space or enter to finish current selection and start a new one, use esc to terminate multiple ROI selection process.

Parameters
windowNamename of the window where selection process will be shown.
imgimage to select a ROI.
boundingBoxesselected ROIs.
showCrosshairif true crosshair of selection rectangle will be shown.
fromCenterif true center of selection will match initial mouse position. In opposite case a corner of selection rectangle will correspont to the initial mouse position.
Note
The function sets it's own mouse callback for specified window using cv::setMouseCallback(windowName, ...). After finish of work an empty callback will be set for the used window.

§ setMouseCallback()

void cv::setMouseCallback ( const String winname,
MouseCallback  onMouse,
void *  userdata = 0 
)

Sets mouse handler for the specified window.

Parameters
winnameName of the window.
onMouseMouse callback. See OpenCV samples, such as https://github.com/opencv/opencv/tree/master/samples/cpp/ffilldemo.cpp, on how to specify and use the callback.
userdataThe optional parameter passed to the callback.
Examples:
camshiftdemo.cpp, ffilldemo.cpp, grabcut.cpp, lkdemo.cpp, warpPerspective_demo.cpp, and watershed.cpp.

§ setTrackbarMax()

void cv::setTrackbarMax ( const String trackbarname,
const String winname,
int  maxval 
)

Sets the trackbar maximum position.

The function sets the maximum position of the specified trackbar in the specified window.

Note

[Qt Backend Only] winname can be empty (or NULL) if the trackbar is attached to the control panel.

Parameters
trackbarnameName of the trackbar.
winnameName of the window that is the parent of trackbar.
maxvalNew maximum position.
Examples:
falsecolor.cpp.

§ setTrackbarMin()

void cv::setTrackbarMin ( const String trackbarname,
const String winname,
int  minval 
)

Sets the trackbar minimum position.

The function sets the minimum position of the specified trackbar in the specified window.

Note

[Qt Backend Only] winname can be empty (or NULL) if the trackbar is attached to the control panel.

Parameters
trackbarnameName of the trackbar.
winnameName of the window that is the parent of trackbar.
minvalNew minimum position.
Examples:
falsecolor.cpp.

§ setTrackbarPos()

void cv::setTrackbarPos ( const String trackbarname,
const String winname,
int  pos 
)

Sets the trackbar position.

The function sets the position of the specified trackbar in the specified window.

Note

[Qt Backend Only] winname can be empty (or NULL) if the trackbar is attached to the control panel.

Parameters
trackbarnameName of the trackbar.
winnameName of the window that is the parent of trackbar.
posNew position.
Examples:
falsecolor.cpp.

§ setWindowProperty()

void cv::setWindowProperty ( const String winname,
int  prop_id,
double  prop_value 
)

Changes parameters of a window dynamically.

The function setWindowProperty enables changing properties of a window.

Parameters
winnameName of the window.
prop_idWindow property to edit. The supported operation flags are: (cv::WindowPropertyFlags)
prop_valueNew value of the window property. The supported flags are: (cv::WindowFlags)

§ setWindowTitle()

void cv::setWindowTitle ( const String winname,
const String title 
)

Updates window title.

Parameters
winnameName of the window.
titleNew title.

§ startWindowThread()

int cv::startWindowThread ( )

§ waitKey()

int cv::waitKey ( int  delay = 0)

Waits for a pressed key.

The function waitKey waits for a key event infinitely (when \(\texttt{delay}\leq 0\) ) or for delay milliseconds, when it is positive. Since the OS has a minimum time between switching threads, the function will not wait exactly delay ms, it will wait at least delay ms, depending on what else is running on your computer at that time. It returns the code of the pressed key or -1 if no key was pressed before the specified time had elapsed.

Note

This function is the only method in HighGUI that can fetch and handle events, so it needs to be called periodically for normal event processing unless HighGUI is used within an environment that takes care of event processing.

Note

The function only works if there is at least one HighGUI window created and the window is active. If there are several HighGUI windows, any of them can be active.

Parameters
delayDelay in milliseconds. 0 is the special value that means "forever".
Examples:
AddingImagesTrackbar.cpp, camshiftdemo.cpp, cloning_demo.cpp, contours2.cpp, convexhull.cpp, copyMakeBorder_demo.cpp, demhist.cpp, distrans.cpp, Drawing_1.cpp, Drawing_2.cpp, edge.cpp, facedetect.cpp, falsecolor.cpp, ffilldemo.cpp, fitellipse.cpp, fld_lines.cpp, grabcut.cpp, hog.cpp, houghcircles.cpp, houghlines.cpp, image_alignment.cpp, kalman.cpp, kmeans.cpp, laplace.cpp, lkdemo.cpp, lsd_lines.cpp, MatchTemplate_Demo.cpp, minarea.cpp, morphology2.cpp, Morphology_1.cpp, npr_demo.cpp, pca.cpp, peopledetect.cpp, polar_transforms.cpp, Pyramids.cpp, segment_objects.cpp, shape_example.cpp, Smoothing.cpp, Sobel_Demo.cpp, train_HOG.cpp, videowriter_basic.cpp, warpPerspective_demo.cpp, and watershed.cpp.

§ waitKeyEx()

int cv::waitKeyEx ( int  delay = 0)

Similar to waitKey, but returns full key code.

Note

Key code is implementation specific and depends on used backend: QT/GTK/Win32/etc