Java 仿射变换:从形状中心缩放形状
我正在尝试使用仿射变换从矩形的中心缩放矩形。我相信解决方案是显而易见的,但我无法让它工作!这是我到目前为止测试的内容Java 仿射变换:从形状中心缩放形状,java,swing,geometry,shape,affinetransform,Java,Swing,Geometry,Shape,Affinetransform,我正在尝试使用仿射变换从矩形的中心缩放矩形。我相信解决方案是显而易见的,但我无法让它工作!这是我到目前为止测试的内容 import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import java.awt.geom.AffineTransform; import javax.swing.JO
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.AffineTransform;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class Test extends JPanel {
Test()
{
super(null);
setOpaque(true);
setBackground(Color.WHITE);
setPreferredSize(new Dimension(200,200));
}
@Override
protected void paintComponent(Graphics g1) {
super.paintComponent(g1);
Rectangle r= new Rectangle(5,5,getWidth()-10,getHeight()-10);
double cx= r.getCenterX();
double cy= r.getCenterY();
Graphics2D g=(Graphics2D)g1;
g.setColor(Color.BLACK);
AffineTransform old= g.getTransform();
for(double zoom=0.9; zoom>=0.5; zoom-=0.1)
{
AffineTransform tr2= new AffineTransform(old);
tr2.translate(-cx, -cy);
tr2.scale(zoom, zoom);
tr2.translate(cx/zoom,cy/zoom);
g.setTransform(tr2);
g.draw(r);
g.setTransform(old);
}
}
public static void main(String[] args) {
JOptionPane.showMessageDialog(null, new Test());
}
}
但它不起作用。。。。有什么建议吗?假设缩放修复了矩形左上角的位置(我认为这是正确的,但我已经很久没有用Java做过图形了),您需要将矩形转换为与缩放相反的方向
tr2.translate(
r.getWidth()*(1-zoom)/2,
r.getHeight()*(1-zoom)/2
);
tr2.scale(zoom,zoom);
g.setTransform(tr2);
因此,将矩形向左上移动一半宽度和高度的变化。这涉及一个称为共轭变换的过程 如果S是要进行的缩放,T是将点(0,0)转换为缩放中心点的变换,则执行此操作的变换是
T(S(逆(T))我明白你在处理矩形时的意思。原因是,转换的初始计算没有考虑容器对象的大小 改用这个:
tr2.translate(
(this.getWidth()/2) - (r.getWidth()*(zoom))/2,
(this.getHeight()/2) - (r.getHeight()*(zoom))/2
);
tr2.scale(zoom,zoom);
g.setTransform(tr2);
这样做的目的是在缩放矩形之前将其平移到面板的中心。在我的测试中,它工作得很好。(稍后)这里有一个解决方案,它在事先不知道面板尺寸的情况下工作
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class Test extends JPanel
{
private static final long serialVersionUID = 1L;
private Test()
{
super(null);
setOpaque(true);
setBackground(Color.WHITE);
setPreferredSize(new Dimension(600,600));
}
@Override
protected void paintComponent(Graphics g1) {
super.paintComponent(g1);
Shape r= new Ellipse2D.Double(5,380,400,200);
double cx= r.getBounds2D().getCenterX();
double cy= r.getBounds2D().getCenterY();
Graphics2D g=(Graphics2D)g1;
g.setColor(Color.BLACK);
AffineTransform old= g.getTransform();
g.drawLine((int)cx-10, (int)cy, (int)cx+10, (int)cy);
g.drawLine((int)cx, (int)cy-10, (int)cx, (int)cy+10);
for(double zoom=1; zoom>=0.1; zoom-=0.1)
{
AffineTransform tr2 =AffineTransform.getTranslateInstance(-cx, -cy);
AffineTransform tr= AffineTransform.getScaleInstance(zoom,zoom);
tr.concatenate(tr2); tr2=tr;
tr =AffineTransform.getTranslateInstance(cx, cy);
tr.concatenate(tr2); tr2=tr;
tr= new AffineTransform(old);
tr.concatenate(tr2); tr2=tr;
g.setTransform(tr2);
g.draw(r);
g.setTransform(old);
}
}
public static void main(String[] args) {
JOptionPane.showMessageDialog(null, new Test());
}
}
我正在开发一个桌面应用程序来裁剪Brittney Spear的脸(D.a.Y.),裁剪矩形必须围绕其中心点缩放:
import javafx.scene.Cursor;
import javafx.scene.Group;
import javafx.scene.input.MouseEvent;
import javafx.scene.input.ScrollEvent;
import javafx.scene.paint.Color;
import javafx.scene.paint.Paint;
import javafx.scene.shape.Rectangle;
class ResizableRectangle extends Rectangle {
ResizableRectangle(double x, double y, double width, double height, Group group) {
super(x, y, width, height);
// Set scroll listener for crop selection
group.addEventHandler(ScrollEvent.SCROLL, event -> {
double zoomFactor = 1.10;
double deltaY = event.getDeltaY();
if (deltaY > 0) {
zoomFactor = 2.0 - zoomFactor;
}
super.setX(getX() + (super.getWidth() * (1 - zoomFactor) / 2)); // Set new X position
super.setWidth(getWidth() * zoomFactor); // Set new Width
super.setY(getY() + (super.getHeight() * (1 - zoomFactor) / 2)); // Set new Y position
super.setHeight(getHeight() * zoomFactor); // Set new Height
event.consume();
});
});
}
通常,该算法的工作原理如下:
- 将矩形x值转换为:
x+(宽度*(1-zoomFactor)/2)
- 将y值转换为:
y+(高度*(1-zoomFactor)/2)
- 将新宽度设置为:
width*zoomFactor
- 将新高度设置为:
height*zoomFactor