如何在 Java 中渲染倾斜的图像？

Question

我的问题是我有一个呈现图像的 Java 应用程序。现在我想渲染一个倾斜的图像。

一种直接的方法是生成一个倾斜的图像然后渲染它，但我的目标是根据窗口中的鼠标移动来倾斜图像。

一个可能的解决方案是在不同的倾斜角度有多个图像并在鼠标移动时渲染它们，但这样的实现在精度上是有限的，并不是我想要的。

有没有办法即时渲染倾斜的图像？

提前致谢。

Answer 1

我认为您需要查看AffineTransform 它有一种旋转形状的方法以及其他变换。

An example of how it can be used can be found here

基本上：

AffineTransform at = AffineTransform.getTranslateInstance(width, height); //Create the AffineTransform instance
at.rotate(someRadianValue); // Apply the transforms you wish
g2.draw(at.createTransformedShape(myShape)); // Draw the transformed shape

Answer 2

我完全同意上一篇文章，AffineTransform 是要走的路。这是一个简单的例子......

import java.awt.*;
import java.awt.geom.*;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;

public class RotateImage {
    private static final int PANEL_WIDTH = 600;
    private static final Dimension MAIN_SIZE = new Dimension(PANEL_WIDTH, PANEL_WIDTH);
    private static final int SLIDER_MIN = -180;
    private static final int SIDER_MAX = 180;
    private static final int MAJOR_TICK = 30;
    private static final int MINOR_TICK = 15;
    private static final String URL_PATH = "http://duke.kenai.com/guitar/DukeAsKeith-daylightSmall.png";

    private JPanel mainPanel = new JPanel();
    private JPanel drawingPanel = createDrawingPanel();
    private AffineTransform transform = new AffineTransform();
    private JSlider rotationSlider;
    private Image image;

    public RotateImage() {
        mainPanel.setLayout(new BorderLayout());
        mainPanel.add(drawingPanel, BorderLayout.CENTER);
        mainPanel.add(createTransformPanel(), BorderLayout.SOUTH);

        URL url;
        try {
            url = new URL(URL_PATH);
            image = ImageIO.read(url ); 
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private JPanel createTransformPanel() {
        rotationSlider = new JSlider(SLIDER_MIN, SIDER_MAX, 0);
        rotationSlider.setMajorTickSpacing(MAJOR_TICK);
        rotationSlider.setMinorTickSpacing(MINOR_TICK);
        rotationSlider.setPaintLabels(true);
        rotationSlider.setPaintTicks(true);
        rotationSlider.setPaintTrack(true);
        rotationSlider.setSnapToTicks(true);
        rotationSlider.addChangeListener(new SliderListener());

        JPanel transformingPanel = new JPanel(new BorderLayout());
        transformingPanel.setBorder(BorderFactory.createEtchedBorder());
        transformingPanel.add(rotationSlider);
        return transformingPanel;
    }

    @SuppressWarnings("serial")
    private JPanel createDrawingPanel() {
        if (drawingPanel != null) {
            return drawingPanel;
        }
        drawingPanel = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                myPaint(g);
            }
        };

        drawingPanel.setPreferredSize(MAIN_SIZE);
        return drawingPanel;
    }

    private void myPaint(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setStroke(new BasicStroke(3));
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        AffineTransform oldTransform = g2.getTransform();
        if (transform != null) {
            g2.setTransform(transform);
        }
        if (image != null) {
            g2.drawImage(image, 70, 70, null);
        }
        g2.setTransform(oldTransform);
    }

    public JComponent getPanel() {
        return mainPanel;
    }

    private class SliderListener implements ChangeListener {
        public void stateChanged(ChangeEvent e) {
            double theta = Math.PI * rotationSlider.getValue() / 180;
            double center = (double) PANEL_WIDTH / 2;
            transform = AffineTransform.getRotateInstance(theta, center, center);
            drawingPanel.repaint();
        }
    }

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("RotateShape Application");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new RotateImage().getPanel());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}