A small snippet to render a rounded QT main window

RoundedMainWindow.h

    void resizeEvent(QResizeEvent* event)
    {
        QImage image(this->size(), QImage::Format_Mono);
        image.fill(0);

        int roundness = 20;

        if (!this->isFullScreen() && !this->isMaximized()) {
            //image.setPixel(0, 0, 1); image.setPixel(1, 0, 1); image.setPixel(2, 0, 1); image.setPixel(3, 0, 1); image.setPixel(4, 0, 1); image.setPixel(5, 0, 1); image.setPixel(6, 0, 1);
            //image.setPixel(0, 1, 1); image.setPixel(1, 1, 1); image.setPixel(2, 1, 1); image.setPixel(3, 1, 1); image.setPixel(4, 1, 1);
            //image.setPixel(0, 2, 1); image.setPixel(1, 2, 1); image.setPixel(2, 2, 1); 
            //image.setPixel(0, 3, 1); image.setPixel(1, 3, 1); image.setPixel(2, 3, 1);
            //image.setPixel(0, 4, 1); 
            //image.setPixel(0, 5, 1);

            for (int x = 0; x < roundness; x++)
            {
                for (int y = 0; y < roundness; y++) {
                    // Remove the pixels along the border
                    if(x == 0 || y == 0)
                        image.setPixel(x, y, 1);

                    // Remove the pixel if it lies outside of the circle at x, y and in the second quadrant of the circle
                    if((x <= roundness && y <= roundness) && (sqrt(pow((double) roundness - x, 2) + pow((double) roundness - y, 2))) >= roundness)
                        image.setPixel(x, y, 1);
                }
            }

       }
        this->setMask(QPixmap::fromImage(image));
    }