JScrollPane setViewPosition After" Zoom" [英] JScrollPane setViewPosition After "Zoom"

问题描述

我这里的代码是使用MouseAdapter来监听用户在他们想要放大的图像区域周围绘制一个框并计算框与图像的比例。然后它将图像调整为计算的比例。这部分有效。

The code that I have here is using a MouseAdapter to listen for the user to "draw" a box around the area of an image that they would like to zoom in on and calculate the ratio of the box to the image. It then resizes the image to the calculated ratio. This part works.

我遇到的问题是，在调整图像大小后，JScrollPane视图看起来好像仍处于同一个左上角位置。我已经尝试了几种似乎已经接近我想要但不完全正确的结果的方法。

The issue that I am having is making the JScrollPane view appear as if it is still at the same top left position after the image has been resized. I have tried several methods that seem to have gotten close to the result I want but not exactly.

这是监听器，它找到比例并设置位置： / p>

This is the Listener that finds the scale ratio and sets the position:

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.Graphics;
import java.awt.Point;

import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.JComponent;

public class DynamicZoom extends MouseAdapter {

private Point start;
private Point end;
private double zoom = 1.0;
private JScrollPane pane;
private JViewport port;


public void mousePressed(MouseEvent e) {
    if(e.getButton() == MouseEvent.BUTTON1) {
        this.pane = (JScrollPane)e.getSource();
        this.port = pane.getViewport();
        start = e.getPoint();
    }
}

public void mouseReleased(MouseEvent e) {
    if(this.pane != null) {
        Point curr = this.port.getViewPosition();
        end = e.getPoint();

        ImageComponent canvas = (ImageComponent)this.port.getView();
        zoom = canvas.getScale();
        double factor = 0.0;
        double selectedWidth = Math.abs(end.getX() - start.getX());
        double selectedHeight = Math.abs(end.getY() - start.getY());
        if(selectedWidth > selectedHeight)
            factor = this.port.getWidth() / selectedWidth;
        else
            factor = this.port.getHeight() / selectedHeight;

        zoom *= factor;
        int x = (int)((start.x+curr.x)*zoom);
        int y = (int)((start.y+curr.y)*zoom);

        Point point = new Point(x, y);

        ((ImageComponent)(this.port.getView())).setScale(zoom);

        ResizeViewport.resize(pane);
        this.port.setViewPosition(point);
    }
}

public void mouseDragged(MouseEvent e) {
    if(this.pane != null) {
        Graphics g = this.port.getGraphics();
        int width = this.start.x - e.getX();
        int height = this.start.y - e.getY();

        int w = Math.abs( width );
        int h = Math.abs( height );
        int x = width < 0 ? this.start.x : e.getX();
        int y = height < 0 ? this.start.y : e.getY();
        g.drawRect(x, y, w, h);
        this.port.repaint();
    }
}

}

这是它调整大小并显示图像的ImageComponent：

This is the ImageComponent it resizes and displays the image:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

import javax.swing.JComponent;

public class ImageComponent extends JComponent {
private static final long serialVersionUID = 1975488835382044371L;
private BufferedImage img = null;

private double scale = 0.0;

public ImageComponent() {}

public ImageComponent(BufferedImage img) {
    this.displayPage(img);
}

@Override
public void paint(Graphics g) {
    Graphics2D g2 = ((Graphics2D)g);
    if(this.img != null) {
        int width = (int)(this.img.getWidth() * this.scale);
        int height = (int)(this.img.getHeight() * this.scale);
        this.setPreferredSize(new Dimension(width, height));
        g2.drawImage(this.img, 0, 0, width, height, null, null);
        g2.dispose();
    }
}

public void displayPage(BufferedImage pic) {
    if(img != null) {
        this.img = pic;
    }
}

public BufferedImage getPage() {
    return this.img;
}

public void setScale(double ratio) {
    if(ratio > .04) {
        this.scale = ratio;
        this.repaint();
    }
}

public double getScale() {
    return this.scale;
}
}

ResizeViewport强制视口显示整个ImageComponent它是按比例放大的，否则会将图像剪裁为之前的大小：

The ResizeViewport forces the viewport to show the entire ImageComponent when it is scaled up because otherwise it will clip the image at the size that it previously was:

import java.awt.Dimension;

import javax.swing.JScrollPane;
public class ResizeViewport {
public static void resize(JScrollPane scroll) {
    int vw = scroll.getWidth()-scroll.getVerticalScrollBar().getWidth();
    int vh = scroll.getHeight()-scroll.getHorizontalScrollBar().getHeight();
    scroll.getViewport().setViewSize(new Dimension(vw, vh));
}
}

推荐答案

它事实证明，用于计算位置的数学或我设计代码的方式没有任何问题。问题是ImageComponent在计算位置时仍在另一个Thread中绘制;因此返回getWidth（）和getHeight（）方法的false值。我使用以下代码解决了这个问题：

It turns out there is nothing wrong with the math used to calculate the position or the way I designed the code. The problem was that the ImageComponent was still painting in another Thread when the position was being calculated; therefore returning "false" values for the getWidth() and getHeight() methods. I solved the issue using the following code:

EventQueue.invokeLater(new Runnable() {
   public void run() {
      port.setViewPosition(new Point(x,y));
   }
});

这样可以在尝试计算图像大小和设置位置之前完成绘画。 JScrollPane中。问题解决了。我还是要感谢那些花时间至少审查这个问题的人。

This allows the painting to finish before trying to calculate the size of the image and setting the position in the JScrollPane. Problem solved. I would still like to throw a thanks out to the people that took the time to at least review this issue.

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