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Qt New Functions
Data Structures | Functions

Qt New Functions
[High-level GUI]

![image](pics/qtgui.png) More...

Data Structures

struct  QtFont
 QtFont available only for Qt. More...

Functions

CV_EXPORTS QtFont fontQt (const String &nameFont, int pointSize=-1, Scalar color=Scalar::all(0), int weight=QT_FONT_NORMAL, int style=QT_STYLE_NORMAL, int spacing=0)
 Creates the font to draw a text on an image.
CV_EXPORTS void addText (const Mat &img, const String &text, Point org, const QtFont &font)
 Draws a text on the image.
CV_EXPORTS void displayOverlay (const String &winname, const String &text, int delayms=0)
 Displays a text on a window image as an overlay for a specified duration.
CV_EXPORTS void displayStatusBar (const String &winname, const String &text, int delayms=0)
 Displays a text on the window statusbar during the specified period of time.
CV_EXPORTS void saveWindowParameters (const String &windowName)
 Saves parameters of the specified window.
CV_EXPORTS void loadWindowParameters (const String &windowName)
 Loads parameters of the specified window.
CV_EXPORTS int createButton (const String &bar_name, ButtonCallback on_change, void *userdata=0, int type=QT_PUSH_BUTTON, bool initial_button_state=false)
 Attaches a button to the control panel.

Detailed Description

![image](pics/qtgui.png)

This figure explains new functionality implemented with Qt\* GUI. The new GUI provides a statusbar, a toolbar, and a control panel. The control panel can have trackbars and buttonbars attached to it. If you cannot see the control panel, press Ctrl+P or right-click any Qt window and select **Display properties window**.

  • To attach a trackbar, the window name parameter must be NULL.
  • To attach a buttonbar, a button must be created. If the last bar attached to the control panel is a buttonbar, the new button is added to the right of the last button. If the last bar attached to the control panel is a trackbar, or the control panel is empty, a new buttonbar is created. Then, a new button is attached to it.

See below the example used to generate the figure: 

        int main(int argc, char *argv[])
        {

            int value = 50;
            int value2 = 0;


            namedWindow("main1",WINDOW_NORMAL);
            namedWindow("main2",WINDOW_AUTOSIZE | CV_GUI_NORMAL);
            createTrackbar( "track1", "main1", &value, 255,  NULL);

            String nameb1 = "button1";
            String nameb2 = "button2";

            createButton(nameb1,callbackButton,&nameb1,QT_CHECKBOX,1);
            createButton(nameb2,callbackButton,NULL,QT_CHECKBOX,0);
            createTrackbar( "track2", NULL, &value2, 255, NULL);
            createButton("button5",callbackButton1,NULL,QT_RADIOBOX,0);
            createButton("button6",callbackButton2,NULL,QT_RADIOBOX,1);

            setMouseCallback( "main2",on_mouse,NULL );

            Mat img1 = imread("files/flower.jpg");
            VideoCapture video;
            video.open("files/hockey.avi");

            Mat img2,img3;

            while( waitKey(33) != 27 )
            {
                img1.convertTo(img2,-1,1,value);
                video >> img3;

                imshow("main1",img2);
                imshow("main2",img3);
            }

            destroyAllWindows();

            return 0;
        }

Function Documentation

CV_EXPORTS void cv::addText ( const Mat &  img,
const String &  text,
Point  org,
const QtFont &  font 
)

Draws a text on the image.

The function addText draws *text* on the image *img* using a specific font *font* (see example cv::fontQt )

Parameters:
img8-bit 3-channel image where the text should be drawn.
textText to write on an image.
orgPoint(x,y) where the text should start on an image.
fontFont to use to draw a text.
CV_EXPORTS int cv::createButton ( const String &  bar_name,
ButtonCallback  on_change,
void *  userdata = 0,
int  type = QT_PUSH_BUTTON,
bool  initial_button_state = false 
)

Attaches a button to the control panel.

The function createButton attaches a button to the control panel. Each button is added to a buttonbar to the right of the last button. A new buttonbar is created if nothing was attached to the control panel before, or if the last element attached to the control panel was a trackbar.

See below various examples of the cv::createButton function call: : 

    createButton(NULL,callbackButton);//create a push button "button 0", that will call callbackButton.
    createButton("button2",callbackButton,NULL,QT_CHECKBOX,0);
    createButton("button3",callbackButton,&value);
    createButton("button5",callbackButton1,NULL,QT_RADIOBOX);
    createButton("button6",callbackButton2,NULL,QT_PUSH_BUTTON,1);
Parameters:
bar_nameName of the button.
on_changePointer to the function to be called every time the button changes its state. This function should be prototyped as void Foo(int state,\*void); . *state* is the current state of the button. It could be -1 for a push button, 0 or 1 for a check/radio box button.
userdataPointer passed to the callback function.
typeOptional type of the button. Available types are: (cv::QtButtonTypes)
initial_button_stateDefault state of the button. Use for checkbox and radiobox. Its value could be 0 or 1. (__Optional__)
CV_EXPORTS void cv::displayOverlay ( const String &  winname,
const String &  text,
int  delayms = 0 
)

Displays a text on a window image as an overlay for a specified duration.

The function displayOverlay displays useful information/tips on top of the window for a certain amount of time *delayms*. The function does not modify the image, displayed in the window, that is, after the specified delay the original content of the window is restored.

Parameters:
winnameName of the window.
textOverlay text to write on a window image.
delaymsThe period (in milliseconds), during which the overlay text is displayed. If this function is called before the previous overlay text timed out, the timer is restarted and the text is updated. If this value is zero, the text never disappears.
CV_EXPORTS void cv::displayStatusBar ( const String &  winname,
const String &  text,
int  delayms = 0 
)

Displays a text on the window statusbar during the specified period of time.

The function displayStatusBar displays useful information/tips on top of the window for a certain amount of time *delayms* . This information is displayed on the window statusbar (the window must be created with the CV_GUI_EXPANDED flags).

Parameters:
winnameName of the window.
textText to write on the window statusbar.
delaymsDuration (in milliseconds) to display the text. If this function is called before the previous text timed out, the timer is restarted and the text is updated. If this value is zero, the text never disappears.
CV_EXPORTS QtFont cv::fontQt ( const String &  nameFont,
int  pointSize = -1,
Scalar  color = Scalar::all(0),
int  weight = QT_FONT_NORMAL,
int  style = QT_STYLE_NORMAL,
int  spacing = 0 
)

Creates the font to draw a text on an image.

The function fontQt creates a cv::QtFont object. This cv::QtFont is not compatible with putText .

A basic usage of this function is the following: : 

    QtFont font = fontQt("Times");
    addText( img1, "Hello World !", Point(50,50), font);
Parameters:
nameFontName of the font. The name should match the name of a system font (such as Times*). If the font is not found, a default one is used.
pointSizeSize of the font. If not specified, equal zero or negative, the point size of the font is set to a system-dependent default value. Generally, this is 12 points.
colorColor of the font in BGRA where A = 255 is fully transparent. Use the macro CV_RGB for simplicity.
weightFont weight. Available operation flags are : cv::QtFontWeights You can also specify a positive integer for better control.
styleFont style. Available operation flags are : cv::QtFontStyles
spacingSpacing between characters. It can be negative or positive.
CV_EXPORTS void cv::loadWindowParameters ( const String &  windowName )

Loads parameters of the specified window.

The function loadWindowParameters loads size, location, flags, trackbars value, zoom and panning location of the window windowName.

Parameters:
windowNameName of the window.
CV_EXPORTS void cv::saveWindowParameters ( const String &  windowName )

Saves parameters of the specified window.

The function saveWindowParameters saves size, location, flags, trackbars value, zoom and panning location of the window windowName.

Parameters:
windowNameName of the window.
Generated on Tue Jul 12 2022 16:42:41 by  doxygen 1.7.2