这是一个基本的例子。
它使用ImagePanel负责渲染图像的特殊功能。它有自己的鼠标监听器来处理光标的变化和调整大小的操作。
缩放算法基于分而治之的方法，以提供相当快速但高质量的缩放。
我还没有完成对角线调整大小，我会把它留给你;）
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Transparency;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
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.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ImageViewer {
public static void main(String[] args) {
new ImageViewer();
}
public ImageViewer() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new ViewPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class ViewPane extends JPanel {
public ViewPane() {
setLayout(null);
ImagePane imagePane = new ImagePane();
imagePane.setSize(imagePane.getPreferredSize());
imagePane.setLocation(0, 0);
add(imagePane);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
public static class ImagePane extends JPanel {
private BufferedImage bg;
private BufferedImage scaled;
public ImagePane() {
try {
bg = ImageIO.read(new File("C:\\hold\\thumbnails\\MT002.jpg"));
scaled = getScaledInstanceToFit(bg, new Dimension(100, 100));
} catch (IOException ex) {
ex.printStackTrace();
}
setBackground(Color.BLACK);
MouseHandler handler = new MouseHandler();
addMouseListener(handler);
addMouseMotionListener(handler);
}
@Override
public Dimension getPreferredSize() {
return bg == null ? new Dimension(200, 200) : new Dimension(scaled.getWidth(), scaled.getHeight());
}
@Override
public void invalidate() {
super.invalidate();
scaled = getScaledInstanceToFit(bg, getSize());
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
int x = (getWidth() - scaled.getWidth()) / 2;
int y = (getHeight() - scaled.getHeight()) / 2;
g2d.drawImage(scaled, x, y, this);
g2d.dispose();
}
public enum MouseAction {
Move(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR)),
ResizeSouth(Cursor.getPredefinedCursor(Cursor.S_RESIZE_CURSOR)),
ResizeNorth(Cursor.getPredefinedCursor(Cursor.N_RESIZE_CURSOR)),
ResizeEast(Cursor.getPredefinedCursor(Cursor.E_RESIZE_CURSOR)),
ResizeWest(Cursor.getPredefinedCursor(Cursor.W_RESIZE_CURSOR)),
ResizeNorthEast(Cursor.getPredefinedCursor(Cursor.NE_RESIZE_CURSOR)),
ResizeNorthWest(Cursor.getPredefinedCursor(Cursor.NW_RESIZE_CURSOR)),
ResizeSouthEast(Cursor.getPredefinedCursor(Cursor.SE_RESIZE_CURSOR)),
ResizeSouthWest(Cursor.getPredefinedCursor(Cursor.SW_RESIZE_CURSOR));
private Cursor cursor;
private MouseAction(Cursor cursor) {
this.cursor = cursor;
}
public Cursor getCursor() {
return cursor;
}
}
public class MouseHandler extends MouseAdapter {
private MouseAction action;
private Point clickPoint;
private Point offset;
private boolean ignoreMoves;
protected void updateAction(MouseEvent e) {
int x = e.getX();
int y = e.getY();
int width = getWidth();
int height = getHeight();
if (x < 10 && y < 10) {
action = MouseAction.ResizeNorthWest;
} else if (x > width - 10 && y < 10) {
action = MouseAction.ResizeNorthWest;
} else if (y < 10) {
action = MouseAction.ResizeNorth;
} else if (x < 10 && y > height - 10) {
action = MouseAction.ResizeSouthWest;
} else if (x > width - 10 && y > height - 10) {
action = MouseAction.ResizeSouthEast;
} else if (y > height - 10) {
action = MouseAction.ResizeSouth;
} else if (x < 10) {
action = MouseAction.ResizeWest;
} else if (x > width - 10) {
action = MouseAction.ResizeEast;
} else {
action = MouseAction.Move;
}
setCursor(action.getCursor());
}
@Override
public void mouseMoved(MouseEvent e) {
if (!ignoreMoves) {
updateAction(e);
}
}
@Override
public void mousePressed(MouseEvent e) {
updateAction(e);
ignoreMoves = true;
clickPoint = e.getPoint();
}
@Override
public void mouseReleased(MouseEvent e) {
clickPoint = null;
ignoreMoves = false;
}
@Override
public void mouseDragged(MouseEvent e) {
switch (action) {
case Move: {
Point p = e.getPoint();
p.x -= clickPoint.x;
p.y -= clickPoint.y;
p = SwingUtilities.convertPoint(ImagePane.this, p, getParent());
setLocation(p);
}
break;
case ResizeWest: {
Point p = e.getPoint();
int xDelta = p.x - clickPoint.x;
int width = getWidth() - xDelta;
int x = getX() + xDelta;
setSize(width, getHeight());
setLocation(x, getY());
revalidate();
}
break;
case ResizeEast: {
Point p = e.getPoint();
int xDelta = p.x - clickPoint.x;
int width = getWidth() + xDelta;
setSize(width, getHeight());
revalidate();
clickPoint = p;
}
break;
case ResizeNorth: {
Point p = e.getPoint();
int yDelta = p.y - clickPoint.y;
int height = getHeight() - yDelta;
int y = getY() + yDelta;
setSize(getWidth(), height);
setLocation(getX(), y);
revalidate();
}
break;
case ResizeSouth: {
Point p = e.getPoint();
int yDelta = p.y - clickPoint.y;
int height = getHeight() + yDelta;
setSize(getWidth(), height);
revalidate();
clickPoint = p;
}
break;
}
}
@Override
public void mouseExited(MouseEvent e) {
}
}
}
public static BufferedImage getScaledInstanceToFit(BufferedImage img, Dimension size) {
double scaleFactor = getScaleFactorToFit(img, size);
return getScaledInstance(img, scaleFactor);
}
public static BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor) {
BufferedImage imgBuffer = null;
imgBuffer = getScaledInstance(img, dScaleFactor, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
return imgBuffer;
}
protected static BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor, Object hint) {
BufferedImage imgScale = img;
int iImageWidth = (int) Math.round(img.getWidth() * dScaleFactor);
int iImageHeight = (int) Math.round(img.getHeight() * dScaleFactor);
if (dScaleFactor <= 1.0d) {
imgScale = getScaledDownInstance(img, iImageWidth, iImageHeight, hint);
} else {
imgScale = getScaledUpInstance(img, iImageWidth, iImageHeight, hint);
}
return imgScale;
}
protected static BufferedImage getScaledDownInstance(BufferedImage img,
int targetWidth,
int targetHeight,
Object hint) {
// System.out.println("Scale down...");
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;
// Use multi-step technique: start with original size, then
// scale down in multiple passes with drawImage()
// until the target size is reached
w = img.getWidth();
h = img.getHeight();
do {
if (w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (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 static BufferedImage getScaledUpInstance(BufferedImage img,
int targetWidth,
int targetHeight,
Object hint) {
int type = BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage) img;
int w, h;
w = img.getWidth();
h = img.getHeight();
do {
if (w < targetWidth) {
w *= 2;
if (w > targetWidth) {
w = targetWidth;
}
}
if (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;
}
public static double getScaleFactorToFit(BufferedImage img, Dimension size) {
double dScale = 1;
if (img != null) {
int imageWidth = img.getWidth();
int imageHeight = img.getHeight();
dScale = getScaleFactorToFit(new Dimension(imageWidth, imageHeight), size);
}
return dScale;
}
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 getScaleFactor(int iMasterSize, int iTargetSize) {
double dScale = 1;
if (iMasterSize > iTargetSize) {
dScale = (double) iTargetSize / (double) iMasterSize;
} else {
dScale = (double) iTargetSize / (double) iMasterSize;
}
return dScale;
}
}
将鼠标侦听器作为视图面板而不是图像面板的一部分会更好，这样您就可以更好地重用两者，但我将把它留给您
注意事项
重要的是要知道，在处理null布局时，您需要负责容器内所有组件的大小和位置。这增加了一些工作量，通常应该避免。