使用 Graphics2D 绘制多条线

Question

我正在尝试开发一个将几何图形绘制到图像上并保存它们的小型应用程序。我的面板类中有这段代码：

@Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        if (getBufferedImage() != null)
        {
            g.drawImage(getBufferedImage(), 120, 0, getBufferedImage().getWidth(), getBufferedImage().getHeight(), null);
        }

        for (Shape s : getShapes())
        {
            if (getBufferedImage() != null)
            {
                Graphics2D graphics = getBufferedImage().createGraphics();
                s.draw(graphics);
            }
        }

    }

getBufferedImage() 将返回加载图像的缓冲图像。而s.draw() 是我定义的各个形状类中的方法。

就像在 Rectangle 中一样，它有代码：graphics.drawRect()
线路：graphics.drawLine()

Line 类中的方法：

@Override
public void draw(Graphics g)
{
    g.setColor(getColor());

    g.drawLine(getXAxis(), getYAxis(), getWidth() + getXAxis(), getHeight() + getYAxis());
}

这些是我重写的 MouseAdapter 方法

@Override
public void mousePressed(MouseEvent event)
{
    switch (getSelectedShape())
    {
        case Rectangle:
        {
            getShapes().add(new Rectangle(event.getX(), event.getY(), getSelectedColor(), isFilled()));
            break;
        }

        case Line:
        {
            getShapes().add(new Line(event.getX(), event.getY(), getSelectedColor()));
            break;
        }
    }

    repaint();
}

@Override
public void mouseDragged(MouseEvent event)
{
    if (event == null || event.getPoint() == null || getShapes().size() <= 0)
    {
        return;
    }

    Shape currentShape = getShapes().get(getShapes().size() - 1);

    if (currentShape == null)
    {
        return;
    }

    currentShape.mouseDragged(event.getPoint());

    repaint();
}

现在，当我绘制任何形状时，会改为绘制多个形状：

Answer 1

给你。

我有一些变量

private boolean start = false;
private ArrayList<Line> shapes = new ArrayList<Line>();
private Line currentLine = null;

添加鼠标处理程序

MouseHandler mouseHandler = new MouseHandler();
addMouseListener(mouseHandler);
addMouseMotionListener(mouseHandler);

MouseHandler 部分。

private class MouseHandler extends MouseAdapter {

        @Override
        public void mousePressed(MouseEvent e) {
            if (e.getButton() == MouseEvent.BUTTON1) {
                start = true;
                currentLine = new Line();
                currentLine.setFirst(new Point(e.getX(), e.getY()));
                currentLine.setLast(new Point(e.getX(), e.getY()));
                shapes.add(currentLine);
            }
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            if (e.getButton() == MouseEvent.BUTTON1) {
                start = false;
                currentLine.setLast(new Point(e.getX(), e.getY()));
                currentLine = null;
                repaint();
            }
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if (start) {
                currentLine.setLast(new Point(e.getX(), e.getY()));
                repaint();
            }
        }
    }

还有颜料

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(Color.black);
    for(Line line : shapes){
        g.drawLine(line.getFirst().x, line.getFirst().y, line.getLast().x, line.getLast().y);
    }
}

用于将其保存到 BufferedImage。

public void saveImage() throws IOException {
   BufferedImage image = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB);
   Graphics2D graphics = image.createGraphics();
   graphics.setColor(Color.black);
   for (Line line : shapes) {
            graphics.drawLine(line.getFirst().x, line.getFirst().y, line.getLast().x, line.getLast().y);
   }
   graphics.dispose();
        ImageIO.write(image, "png", new File("Beniton drawing.png"));

}

添加一个按钮并调用 saveImage()

Answer 2

从绘制代码中拆分 BufferedImage 的创建。

@Override
public void paintComponent(Graphics g)
{
    Graphics2D graphics = (Graphics2D) g;
    for (Shape s : getShapes()) {
        graphics.draw(shape);
    }
}

public void saveAsImage()
{
    if (bufferedImage == null) {
        // Create bufferedImage
    }

    Graphics2D graphics = nufferedImage.createGraphics();
    paint(graphics);           
    graphics.dispose();
}

当然你也可以在paintComponent中只绘制bufferedImage，并在添加一个形状时创建一个新的bufferedImage，虽然这看起来效率低下，容易出错（当布局到其他尺寸时）。

除了需要的Graphics.dispose，代码不遵守“快速绘制没有副作用。”