Java：保持JPanel背景图像的宽高比

java background-image swing jpanel aspect-ratio

2022-09-01 18:22:48

我有一个带有绘画背景图像和一个布局管理器，其中包含其他较小的图像，所有这些都在.背景图像非常大，我希望能够让它保持其宽高比，无论是在大显示器上还是在小显示器上。JPanelJFrame

最终，我希望能够将我和其单元格中的较小图像“粘合”到背景图片上。LayoutManager

我四处寻找资源，似乎很多例子都使用a，但我不是;这会造成问题吗？我会在下面发布我的代码来绘制图像，如果我缺少任何信息，请让我知道。BufferedImage

public class MonitorPanel extends JPanel {
    Image img;
    public MonitorPanel() throws MalformedURLException {
        //add components

        try {
            img = ImageIO.read(new File("src/customer_vlans.jpg"));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
protected void paintComponent(Graphics g)
{
    //paint background image
    super.paintComponent(g);
    //g.drawImage(img, 0, 0, getWidth(), getHeight(), this);
    g.drawImage(img, 0, 0, this);

}

}

编辑：我应该提到，我知道宽高比公式：原始高度/原始宽度x新宽度=新高度但是，我不知道如何正确使用它来发挥我的优势。

答案 1

好吧，最快，最简单的解决方案是使用Image.getScaledInstance

g.drawImage(img.getScaledInstance(newWidth, -1, Image. SCALE_SMOOTH), x, y, this);

如果你想知道负数，java文档说：

如果宽度或高度为负数，则替换一个值以保持原始图像尺寸的纵横比。如果宽度和高度均为负数，则使用原始图像尺寸。

更新

只是作为旁注（我的谷歌正在播放）。

getScaledInstance既不是最快也不是最高质量的方法，但它是最容易的。

阅读The Perils of Image.getScaledInstance，了解更多想法

更新

缩放图像以适合某个区域比简单地缩放纵横比稍微复杂一些。您必须选择是否希望图像“适合”该区域（可能在其周围留下空白区域）或“填充”该区域（以便其最小尺寸适合该区域的最大尺寸）。

Fit Fill

Fit & Fill

基本上，我使用比例因子

这将返回特定大小的比例因子。我用它来根据我需要的算法来决定我要使用哪个因素

public static double getScaleFactor(int iMasterSize, int iTargetSize) {

    double dScale = 1;
    if (iMasterSize > iTargetSize) {

        dScale = (double) iTargetSize / (double) iMasterSize;

    } else {

        dScale = (double) iTargetSize / (double) iMasterSize;

    }

    return dScale;

}

它由这两种方法使用。他们只需要两秒钟。原始和目标。Dimension

public static double getScaleFactorToFit(Dimension original, Dimension toFit) {

    double dScale = 1d;

    if (original != null && toFit != null) {

        double dScaleWidth = getScaleFactor(original.width, toFit.width);
        double dScaleHeight = getScaleFactor(original.height, toFit.height);

        dScale = Math.min(dScaleHeight, dScaleWidth);

    }

    return dScale;

}

public static double getScaleFactorToFill(Dimension masterSize, Dimension targetSize) {

    double dScaleWidth = getScaleFactor(masterSize.width, targetSize.width);
    double dScaleHeight = getScaleFactor(masterSize.height, targetSize.height);

    double dScale = Math.max(dScaleHeight, dScaleWidth);

    return dScale;

}

将图像传递到其中相对简单（直接或通过支持方法）。例如，您可以从方法中调用它paint

double factor getScaledFactorToFit(new Dimension(image.getWidth(), image.getHeight()), getSize());

int scaledWidth = image.getWidth() * scale;
int scaledHeight *= image.getWidth() * scale;

这将自动为您处理宽高比;)

使用扩展的示例进行了更新

public double getScaleFactor(int iMasterSize, int iTargetSize) {

    double dScale = 1;
    if (iMasterSize > iTargetSize) {

        dScale = (double) iTargetSize / (double) iMasterSize;

    } else {

        dScale = (double) iTargetSize / (double) iMasterSize;

    }

    return dScale;

}

public double getScaleFactorToFit(Dimension original, Dimension toFit) {

    double dScale = 1d;

    if (original != null && toFit != null) {

        double dScaleWidth = getScaleFactor(original.width, toFit.width);
        double dScaleHeight = getScaleFactor(original.height, toFit.height);

        dScale = Math.min(dScaleHeight, dScaleWidth);

    }

    return dScale;

}

@Override
protected void paintComponent(Graphics g) {

    super.paintComponent(g);

    double scaleFactor = Math.min(1d, getScaleFactorToFit(new Dimension(image.getWidth(), image.getHeight()), getSize()));

    int scaleWidth = (int) Math.round(image.getWidth() * scaleFactor);
    int scaleHeight = (int) Math.round(image.getHeight() * scaleFactor);

    Image scaled = image.getScaledInstance(scaleWidth, scaleHeight, Image.SCALE_SMOOTH);

    int width = getWidth() - 1;
    int height = getHeight() - 1;

    int x = (width - scaled.getWidth(this)) / 2;
    int y = (height - scaled.getHeight(this)) / 2;

    g.drawImage(scaled, x, y, this);

}

答案 2

试试下面这样：

import java.awt.*;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class SG2B2 {

    JFrame frame;

    public static void main(String[] args) {
        SG2B2 gui = new SG2B2();
        gui.createUI();
    }

    public void createUI() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        MyDrawPanel drawPanel = new MyDrawPanel();
        frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
        frame.setSize(300, 400);
        frame.setVisible(true);
    }

    class MyDrawPanel extends JPanel {

        Image image;
        private final String pic = "Logo.jpg";

        public MyDrawPanel() {
            image = new ImageIcon(pic).getImage();
            image = scaleImage(image);
        }

        @Override
        public void paintComponent(Graphics g) {
            Graphics2D g2 = (Graphics2D) g;
            g2.drawImage(image, 0, 0, this);
        }

        private Image scaleImage(Image rawImage) {
            Image scaledImage = null;
            System.out.println("Scaling");
            try {
                int rawImageWidth = rawImage.getWidth(this);
                int rawImageHeight = rawImage.getHeight(this);
                int paneWidth = (int) getWidth();
                int paneHeight = (int) getHeight();
                System.out.println("Image W = " + rawImageWidth
                        + ", H = " + rawImageHeight
                        + "; Pane W = " + paneWidth
                        + ", H = " + paneHeight);
                // preserve the original ratio  
                float widthRatio = (float) rawImageWidth / (float) paneWidth;
                float heightRatio = (float) rawImageHeight / (float) paneHeight;
                int widthFactor = -1;
                int heightFactor = -1;
                if ((widthRatio > heightRatio) && (widthRatio > 1.0)) {
                    widthFactor = paneWidth;
                } else if ((heightRatio > widthRatio) && (heightRatio > 1.0)) {
                    heightFactor = paneHeight;
                }
                System.out.println("widthRatio = "
                        + String.format("%.3f", widthRatio)
                        + ", heightRatio = "
                        + String.format("%.3f", heightRatio));
                System.out.println("widthFactor = " + widthFactor
                        + ", heightFactor = " + heightFactor);
                if ((widthFactor < 0) && (heightFactor < 0)) {
                    scaledImage = rawImage;
                } else {
                    scaledImage = rawImage.getScaledInstance(widthFactor, heightFactor,
                            Image.SCALE_SMOOTH);
                    // load the new image, 'getScaledInstance' loads asynchronously  
                    MediaTracker tracker = new MediaTracker(this);
                    tracker.addImage(scaledImage, 0);
                    tracker.waitForID(0);
                }
            } catch (InterruptedException ie) {
                System.err.println("load interrupt: " + ie.getMessage());
            } catch (Exception e) {
                e.printStackTrace();
            }
            return (scaledImage);
        }
    }
}

最终将使用将图像缩放到的大小JPanelgetScaledInstance(int width, int height, ImageObserver io)