Creates a trackbar and attaches it to the specified window.
int createTrackbar
(const string& trackbarname, const string& winname, int* value, int count, TrackbarCallback onChange=0, void* userdata=0)¶
int cvCreateTrackbar
(const char* trackbar_name, const char* window_name, int* value, int count, CvTrackbarCallback on_change=NULL )¶
cv.
CreateTrackbar
(trackbarName, windowName, value, count, onChange) → None¶Parameters: |
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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.
Note
Returns the trackbar position.
int getTrackbarPos
(const string& trackbarname, const string& winname)¶
cv2.
getTrackbarPos
(trackbarname, winname) → retval¶
int cvGetTrackbarPos
(const char* trackbar_name, const char* window_name)¶
cv.
GetTrackbarPos
(trackbarName, windowName) → retval¶Parameters: |
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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.
Displays an image in the specified window.
void imshow
(const string& winname, InputArray mat)¶
cv2.
imshow
(winname, mat) → None¶
void cvShowImage
(const char* name, const CvArr* image)¶
cv.
ShowImage
(name, image) → None¶Parameters: |
|
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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 floating-point, the pixel values are multiplied by 255. That is, the value range [0,1] is mapped to [0,255].
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
.
If window was created with OpenGL support, imshow
also support ogl::Buffer
, ogl::Texture2D
and gpu::GpuMat
as input.
Note
This function should be followed by 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.
Creates a window.
void namedWindow
(const string& winname, int flags=WINDOW_AUTOSIZE )¶
cv2.
namedWindow
(winname[, flags]) → None¶
int cvNamedWindow
(const char* name, int flags=CV_WINDOW_AUTOSIZE )¶
cv.
NamedWindow
(name, flags=CV_WINDOW_AUTOSIZE) → None¶Parameters: |
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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 destroyWindow()
or 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:
- CV_WINDOW_NORMAL or CV_WINDOW_AUTOSIZE:
CV_WINDOW_NORMAL
enables you to resize the window, whereasCV_WINDOW_AUTOSIZE
adjusts automatically the window size to fit the displayed image (seeimshow()
), and you cannot change the window size manually.- CV_WINDOW_FREERATIO or CV_WINDOW_KEEPRATIO:
CV_WINDOW_FREERATIO
adjusts the image with no respect to its ratio, whereasCV_WINDOW_KEEPRATIO
keeps the image ratio.- CV_GUI_NORMAL or CV_GUI_EXPANDED:
CV_GUI_NORMAL
is the old way to draw the window without statusbar and toolbar, whereasCV_GUI_EXPANDED
is a new enhanced GUI.
By default, flags == CV_WINDOW_AUTOSIZE | CV_WINDOW_KEEPRATIO | CV_GUI_EXPANDED
Destroys a window.
void destroyWindow
(const string& winname)¶
cv2.
destroyWindow
(winname) → None¶
void cvDestroyWindow
(const char* name)¶
cv.
DestroyWindow
(name) → None¶Parameters: | winname – Name of the window to be destroyed. |
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The function destroyWindow
destroys the window with the given name.
Destroys all of the HighGUI windows.
void destroyAllWindows
()¶
cv2.
destroyAllWindows
() → None¶
void cvDestroyAllWindows
()¶
cv.
DestroyAllWindows
() → None¶The function destroyAllWindows
destroys all of the opened HighGUI windows.
Moves window to the specified position
void moveWindow
(const string& winname, int x, int y)¶
cv2.
moveWindow
(winname, x, y) → None¶
void cvMoveWindow
(const char* name, int x, int y)¶
cv.
MoveWindow
(name, x, y) → None¶Parameters: |
|
---|
Resizes window to the specified size
void resizeWindow
(const string& winname, int width, int height)¶
cv2.
resizeWindow
(winname, width, height) → None¶
void cvResizeWindow
(const char* name, int width, int height)¶
cv.
ResizeWindow
(name, width, height) → None¶Parameters: |
|
---|
Note
Sets mouse handler for the specified window
void setMouseCallback
(const string& winname, MouseCallback onMouse, void* userdata=0 )¶
void cvSetMouseCallback
(const char* window_name, CvMouseCallback on_mouse, void* param=NULL )¶
cv.
SetMouseCallback
(windowName, onMouse, param=None) → None¶Parameters: |
|
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Sets the trackbar position.
void setTrackbarPos
(const string& trackbarname, const string& winname, int pos)¶
cv2.
setTrackbarPos
(trackbarname, winname, pos) → None¶
void cvSetTrackbarPos
(const char* trackbar_name, const char* window_name, int pos)¶
cv.
SetTrackbarPos
(trackbarName, windowName, pos) → None¶Parameters: |
|
---|
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.
Waits for a pressed key.
int waitKey
(int delay=0)¶
cv2.
waitKey
([delay]) → retval¶
int cvWaitKey
(int delay=0 )¶
cv.
WaitKey
(delay=0) → int¶Parameters: | delay – Delay in milliseconds. 0 is the special value that means “forever”. |
---|
The function waitKey
waits for a key event infinitely (when
) 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.
Set OpenGL render handler for the specified window.
void setOpenGlDrawCallback
(const string& winname, OpenGlDrawCallback onOpenGlDraw, void* userdata=0)¶Parameters: |
|
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Sets the specified window as current OpenGL context.
void setOpenGlContext
(const string& winname)¶Parameters: |
|
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Force window to redraw its context and call draw callback ( setOpenGlDrawCallback()
).
void updateWindow
(const string& winname)¶Parameters: |
|
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