我想调整 logo2.png 的大小，使其完全适合 jFrame。谁能帮帮我？
jLabel2 = new javax.swing.JLabel();
jLabel2.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Banking/logo2.png"))); // NOI18N
JDesktopPane.add(jLabel2);
jLabel2.setBounds(0, 0, 500, 290);
【问题讨论】：
JLabel。 JLabel 不会调整图片大小
JLabel 不会重新调整它的内容（即图像），为此，你将不得不让你的手有点脏......
有多种方法可以实现这一目标。就我个人而言，我会从一个自定义组件开始，它从 JPanel 之类的东西扩展而来，它采用基础图像并能够对其进行缩放和绘制。
查看Performing Custom Painting 和Painting in AWT and Swing 了解有关执行自定义绘画的更多详细信息。
缩放图像并不像看起来那么简单，虽然 Java 确实提供了一些 API 来缩放图像，但通常它们不会产生出色的结果。请查看Quality of Image after resize very low -- Java 和The Perils of Image.getScaledInstance() 了解更多详情。
我通常建议看一下imgscalr 库，因为它的结果通常相当好（比基本 Java API 提供的更好，或者我已经通过大多数其他方法看到了），但是对于这个例子，我'已经包含了一个分而治之方法的示例。
此示例提供了“按比例填充”实现，这可确保生成的图像始终填充可用空间，同时保持其纵横比，有关该主题的更多讨论，请参阅 Java: maintaining aspect ratio of JPanel background image
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.HeadlessException;
import java.awt.RenderingHints;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ScaledBackground {
public static void main(String[] args) {
new ScaledBackground();
}
public ScaledBackground() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
try {
BufferedImage img = ImageIO.read(...);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new ImagePane(img));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
});
}
public class ImagePane extends JPanel {
private BufferedImage original;
private BufferedImage scaled;
public ImagePane(BufferedImage img) {
original = img;
scaled = original;
}
@Override
public Dimension getPreferredSize() {
return original == null ? new Dimension(200, 200) : new Dimension(original.getWidth(), original.getHeight());
}
@Override
public void invalidate() {
super.invalidate();
generateScaledInstance();
}
protected void generateScaledInstance() {
if (original != null) {
scaled = getScaledInstanceToFill(original, getSize());
}
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
if (scaled != null) {
int x = (getWidth() - scaled.getWidth()) / 2;
int y = (getHeight() - scaled.getHeight()) / 2;
g2d.drawImage(scaled, x, y, this);
}
g2d.dispose();
}
public BufferedImage getScaledInstanceToFill(BufferedImage img, Dimension size) {
float scaleFactor = getScaleFactorToFill(img, size);
return getScaledInstance(img, scaleFactor);
}
public float getScaleFactorToFill(BufferedImage img, Dimension size) {
float scale = 1f;
if (img != null) {
int imageWidth = img.getWidth();
int imageHeight = img.getHeight();
scale = getScaleFactorToFill(new Dimension(imageWidth, imageHeight), size);
}
return scale;
}
public float getScaleFactorToFill(Dimension original, Dimension toFit) {
float scale = 1f;
if (original != null && toFit != null) {
float dScaleWidth = getScaleFactor(original.width, toFit.width);
float dScaleHeight = getScaleFactor(original.height, toFit.height);
scale = Math.max(dScaleHeight, dScaleWidth);
}
return scale;
}
public float getScaleFactor(int iMasterSize, int iTargetSize) {
float scale = 1;
if (iMasterSize > iTargetSize) {
scale = (float) iTargetSize / (float) iMasterSize;
} else {
scale = (float) iTargetSize / (float) iMasterSize;
}
return scale;
}
public BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor) {
BufferedImage imgBuffer = null;
imgBuffer = getScaledInstance(img, dScaleFactor, RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
return imgBuffer;
}
protected BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor, Object hint, boolean higherQuality) {
BufferedImage scaled = img;
if (dScaleFactor != 1.0) {
if (dScaleFactor > 1.0) {
scaled = getScaledUpInstance(img, dScaleFactor, hint, higherQuality);
} else if (dScaleFactor > 0.0) {
scaled = getScaledDownInstance(img, dScaleFactor, hint, higherQuality);
}
}
return scaled;
}
protected BufferedImage getScaledDownInstance(BufferedImage img, double dScaleFactor, Object hint, boolean higherQuality) {
int targetWidth = (int) Math.round(img.getWidth() * dScaleFactor);
int targetHeight = (int) Math.round(img.getHeight() * dScaleFactor);
int type = (img.getTransparency() == Transparency.OPAQUE)
? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage) img;
if (targetHeight > 0 || targetWidth > 0) {
int w, h;
if (higherQuality) {
w = img.getWidth();
h = img.getHeight();
} else {
w = targetWidth;
h = targetHeight;
}
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
BufferedImage tmp = new BufferedImage(Math.max(w, 1), Math.max(h, 1), type);
Graphics2D g2 = tmp.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
g2.drawImage(ret, 0, 0, w, h, null);
g2.dispose();
ret = tmp;
} while (w != targetWidth || h != targetHeight);
} else {
ret = new BufferedImage(1, 1, type);
}
return ret;
}
protected BufferedImage getScaledUpInstance(BufferedImage img,
double dScaleFactor,
Object hint,
boolean higherQuality) {
int targetWidth = (int) Math.round(img.getWidth() * dScaleFactor);
int targetHeight = (int) Math.round(img.getHeight() * dScaleFactor);
int type = BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage) img;
int w, h;
if (higherQuality) {
w = img.getWidth();
h = img.getHeight();
} else {
w = targetWidth;
h = targetHeight;
}
do {
if (higherQuality && w < targetWidth) {
w *= 2;
if (w > targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h < targetHeight) {
h *= 2;
if (h > targetHeight) {
h = targetHeight;
}
}
BufferedImage tmp = new BufferedImage(w, h, type);
Graphics2D g2 = tmp.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
g2.drawImage(ret, 0, 0, w, h, null);
g2.dispose();
ret = tmp;
tmp = null;
} while (w != targetWidth || h != targetHeight);
return ret;
}
}
}
此示例将随着面板可用空间量的变化而随着图像的变化而增大和缩小
【讨论】：
【讨论】：
先获取Image，然后使用这个方法：
yourImage.getScaledInstance(newWidth, newHeight, Image.SCALE_DEFAULT);
您可以从 JFrame 中获取宽度和高度。然后你可以将Image转换为ImageIcon并添加它。
【讨论】：