我想调整logo2.png的大小，使其完全适合jFrame。任何人都可以帮助我吗？
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);
答案 0 :(得分：2)
JLabel没有重新缩放它的内容（即图像），为此，你将不得不让你的手有点脏......
有很多方法可以实现这一目标。就个人而言，我从一个自定义组件开始，该组件从JPanel扩展而来，它采用基本图像并且能够缩放和绘制它。
有关执行自定义绘画的详细信息，请查看Performing Custom Painting和Painting in AWT and Swing。
缩放图像并不像看起来那么简单，而Java确实提供了一些API来缩放图像，通常，它们不会产生出色的结果。有关详细信息，请查看Quality of Image after resize very low -- Java和The Perils of Image.getScaledInstance()。
我通常建议您查看imgscalr库，因为它的结果通常非常好（比基本Java API提供的更好，或者我通过大多数其他方法看到的更好），但对于此示例，我已经列举了一个分歧的例子。
此示例提供了“缩放以填充”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，有关此主题的更多讨论，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;
}
}
}
此示例将随着图像的变化而增长和缩小，作为面板可用空间量的变化
答案 1 :(得分：2)
答案 2 :(得分：0)
首先获取Image，然后使用此方法：
yourImage.getScaledInstance(newWidth, newHeight, Image.SCALE_DEFAULT);
您可以从JFrame获取宽度和高度。然后，您可以将Image转换为ImageIcon并添加它。