Question

我只是想知道如何使用JLabel组件的paintComponent（）方法旋转矩形图像并正确设置其新的宽度和高度？

我试图旋转（参见附图）并且图像比例变得更大但是JLabel比例保持相同的原因使图像超出JLabel界限或者S：所以我的问题是如何将图像新的宽度和高度设置为组件以更优化的方式动态生成？

enter image description here

Answer 1

+1给MadProgrammers评论和链接。

使用链接中的方法（略微编辑以省略GraphicsConfiguration，drawRenderImage(..)和更改变量名称的使用）：

//https://stackoverflow.com/questions/4156518/rotate-an-image-in-java
public static BufferedImage createTransformedImage(BufferedImage image, double angle) {
    double sin = Math.abs(Math.sin(angle));
    double cos = Math.abs(Math.cos(angle));
    int originalWidth = image.getWidth();
    int originalHeight = image.getHeight();
    int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
    int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
    BufferedImage rotatedBI = new BufferedImage(newWidth, newHeight, BufferedImage.TRANSLUCENT);
    Graphics2D g2d = rotatedBI.createGraphics();
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.translate((newWidth - originalWidth) / 2, (newHeight - originalHeight) / 2);
    g2d.rotate(angle, originalWidth / 2, originalHeight / 2);
    g2d.drawImage(image, 0, 0, null);
    g2d.dispose();
    return rotatedBI;
}

以下是一个例子：

enter image description here

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class RotateImage {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new MyRotatableImage(createImage(), -45));
                frame.pack();
                frame.setVisible(true);
            }
        });
    }

    public static BufferedImage createImage() {
        BufferedImage img = new BufferedImage(100, 50, BufferedImage.TRANSLUCENT);
        Graphics2D g2d = img.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, img.getWidth(), img.getHeight());
        g2d.setColor(Color.BLACK);
        g2d.setFont(new Font("Calibri", Font.BOLD, 20));
        FontMetrics fm = g2d.getFontMetrics();
        String text = "Hello world";
        int textWidth = fm.stringWidth(text);
        g2d.drawString(text, (img.getWidth() / 2) - textWidth / 2, img.getHeight() / 2);
        g2d.dispose();
        return img;
    }
}

class MyRotatableImage extends JPanel {

    private BufferedImage transformedImage;

    public MyRotatableImage(BufferedImage img, int angle) {
        transformedImage = createTransformedImage(img, angle);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.drawImage(transformedImage, 0, 0, null);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(transformedImage.getWidth(), transformedImage.getHeight());
    }

    //https://stackoverflow.com/questions/4156518/rotate-an-image-in-java
    public static BufferedImage createTransformedImage(BufferedImage image, double angle) {
        double sin = Math.abs(Math.sin(angle));
        double cos = Math.abs(Math.cos(angle));
        int originalWidth = image.getWidth();
        int originalHeight = image.getHeight();
        int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
        int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
        BufferedImage rotatedBI = new BufferedImage(newWidth, newHeight, BufferedImage.TRANSLUCENT);
        Graphics2D g2d = rotatedBI.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.translate((newWidth - originalWidth) / 2, (newHeight - originalHeight) / 2);
        g2d.rotate(angle, originalWidth / 2, originalHeight / 2);
        g2d.drawImage(image, 0, 0, null);
        g2d.dispose();
        return rotatedBI;
    }
}

<强>参考：

Rotate an image in java

Answer 2

好的，所以你希望JLabel保持其尺寸并改为调整图像大小。

你可能已经在使用仿射变换，所以你可以使用一些三角函数和最小/最大来找到旋转图像的AABB。适当缩放（我假设您已经使用仿射变换进行旋转）

编辑：

AABB = Axis Aligned Bounding Box，其边对应于旋转图像的最小/最大x，y坐标。只是一种更简洁的说法。

Answer 3

好的，我试过了 David Kroukamp 向我展示的示例。谢谢，大卫，你指出我正确的方向。我认为可以依靠a really good snippet。

public static BufferedImage rotateImage(Image image, int angle)
    {
        double sin = Math.abs(Math.sin(angle));
        double cos = Math.abs(Math.cos(angle));
        int originalWidth = image.getWidth(null);
        int originalHeight = image.getHeight(null);
        int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
        int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
        BufferedImage rotatedBI = new BufferedImage(newWidth, newHeight, BufferedImage.TRANSLUCENT);
        Graphics2D g2d = rotatedBI.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.translate((newWidth - originalWidth) / 2, (newHeight - originalHeight) / 2);
        g2d.rotate(angle, originalWidth / 2, originalHeight / 2);
        g2d.drawImage(image, 0, 0, null);
        g2d.dispose();
        return rotatedBI;
    }

David Kroukamp's result image preview

我测试了片段，结果图像+其组件的比例实际上是动态变化的。 但是我得到的结果组件宽度总是比它的内部图像宽一点：S

例如，这是我以45度角旋转的图像版本

snippet based result image

...正如我所能找到的（在蓝色背景上）它的宽度并不完全适合环绕白色图像......实际上我正在寻找某种标准Java图像处理旋转解决方案但是我找不到它:(所以我不得不深入研究这个问题，至少弄清楚如何解决'更广泛的效果'和避免每次重新绘制时创建新的BufferedImage对象 ......

好的，作为我研究的一部分，我试着写一些我的旋转代码改编。这是：

<强>＆GT;测试

public static void rotateImage(Graphics g, Image image,int tilt,JComponent component)
    {

        // create the transform, note that the transformations happen

                  // in reversed order (so check them backwards)
                  AffineTransform at = new AffineTransform();

                  //5. modify component scale ...

                  double sin = Math.abs(Math.sin(Math.toRadians(tilt)));
                  double cos = Math.abs(Math.cos(Math.toRadians(tilt)));

                  int w=image.getWidth(null);
                  int h=image.getHeight(null);
                  int newW=(int) Math.floor(w * cos + h * sin);
                  int newH=(int) Math.floor(h * cos + w * sin);

                  component.setSize(newW, newH);

                  int width=component.getWidth();
                  int height=component.getHeight();

                  // 4. translate it to the center of the component
                  at.translate(width / 2, height / 2);

                  // 3. do the actual rotation
                  at.rotate(Math.toRadians(tilt));

                  // 2. just a scale because this image is big
    //              at.scale(1, 1);


                  // 1. translate the object so that you rotate it around the
                  //    center (easier :))
                  at.translate(-image.getWidth(null)/2, -image.getHeight(null)/2);



                  // draw the image
                  ((Graphics2D) g).drawImage(image, at, null);


        }

...所以结果图像在-30度倾斜时旋转看起来像这样

enter image description here

我非常希望这一小贴士节省一天：）

谢谢大家的帮助

在覆盖paintComponent（...）方法中旋转图像

3 个答案: