example_selectbox.cpp

This is an example of how to use the SelectionBox Widget.

#include "canvascv/canvas.h"

// These are used to create widgets
#include "canvascv/widgets/selectionbox.h"

#include <iostream>
#include <iterator>

#include <opencv2/highgui.hpp>

using namespace std;
using namespace cv;
using namespace canvascv;

shared_ptr<SelectionBox> selectionBox;

// This is needed for user interaction - creating/editing choosing shapes.
// Clicking on interactive widgets.
// We don't need this code if we only want to display "on screen" messages and "status bar" messages.
// see also Canvas::setMouseCallback()
static void mouseCB(int event, int x, int y, int flags, void* userData) {
    (void)flags;
    Canvas *pCanvas=reinterpret_cast<Canvas*>(userData);
    Point pos(x,y);
    switch( event )
    {
    case EVENT_LBUTTONDOWN:
        if (selectionBox->getVisible() == false)
        {
            selectionBox->setLocation(pos);
            selectionBox->setVisible(true);
        }
        else if (! pCanvas->onMousePress(pos))
        {
            selectionBox->setLocation(pos);
        }
        break;
    case EVENT_LBUTTONUP:
        pCanvas->onMouseRelease(pos);
        break;
    case EVENT_MOUSEMOVE:
        pCanvas->onMouseMove(pos);
        break;
    }
}

int main(int argc, char **argv)
{
    --argc;
    ++argv;
    Mat image;
    if (argc)
    {
        Mat orig = imread(argv[0]);
        if (orig.empty())
        {
            Canvas::fatal(string("Cannot load image ") + argv[0], -1);
        }
        if (orig.cols > 1024)
        {
            double ratio = 1024. / orig.cols;
            cv::resize(orig, image, Size(), ratio, ratio);
        }
        else
        {
            image = orig;
        }
    }
    else
    {
        Canvas::fatal("Must get a path to an image as a parameter" , -1);
    }

    Canvas c("Canvas", image.size());
    selectionBox = SelectionBox::create(c, {
                                            "Long Option1",     // index 0
                                            "Option2\n2 lines", // index 1
                                            "Option3"           // index 2
                                        }, [&c](Widget *w, int i) {
            w->setVisible(false);
            cout << "Option " << i << " was chosen" << endl;
            SelectionBox *sb = (SelectionBox*)w;
            c.setScreenText(CCV_STR("User selected option '" << i<< "': '" << sb->getTextAt(i) << "'\n" <<
                                    "left click to open selection box. left click to select an item\n'q' to quit"));
});
    selectionBox->setVisible(false);

    namedWindow("Canvas", WINDOW_AUTOSIZE);
    setMouseCallback("Canvas", mouseCB, &c);

    c.enableScreenText();
    c.setScreenText("left click to open selection box. left click to select an item\n'q' to quit");

    int key = 0;
    Mat out; // keeping it out of the loop is a little more efficient
    while (key != 'q')
    {
        c.redrawOn(image, out);
        imshow("Canvas", out);
        key = c.waitKeyEx(); // GUI and callbacks happen here
    }

    destroyAllWindows();
    return 0;
}