问用Java将多边形拉伸到其他多边形
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Stack Overflow用户

提问于 2013-05-25 08:52:08

回答 4查看 1.8K关注 0票数 4

我的问题是，我有一个带有小透视图的矩形，我想将其向后拉伸，以再次显示为矩形。

为了直观地表示它，我目前在我的图像中有类似红色形状的东西，我有4个Points (这个形状的每个角)。因此，我希望拥有类似于蓝色形状的东西，并且我已经有了它的Rectangle对象。

我想知道是否有一种方法可以复制一个多边形，并将其绘制为另一个拉伸的多边形。我找到了适用于Android (setPolyToPoly)的东西，但我找不到适用于java的类似这样的东西。

有没有一些参考或代码样本来执行这个操作，或者可能有一些想法可以解决这个问题？

graphics

java-2d

java

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回答 4

Stack Overflow用户

回答已采纳

发布于 2013-05-28 16:49:27

我想我知道你需要什么:一种可以应用于图像的所谓透视变换。Java有内置的AffineTransform，但是仿射转换总是保留行的“并行度”，所以您不能使用它。

现在，如果你在网络上搜索"java透视图转换“，你会发现很多选项，比如JavaFX PerspectiveTransform，JAI PerspectiveTransform。如果您只需要拉伸图像，您也可以使用JHLabs PerspectiveFilter，还有其他选项。

票数 3

Stack Overflow用户

发布于 2013-05-25 18:11:20

下面是一些代码，可以将一个有四个点的多边形拉伸成一个矩形。

public static Rectangle2D polyToRect(Polygon polygon) {
    if (polygon.xpoints.length != 4 || polygon.ypoints.length != 4)
        throw new IllegalArgumentException(
                "More than four points, this cannot be fitted to a rectangle");


    Rectangle2D rect = new Rectangle2D.Double();
    for (int i = 0; i < 4; i++) {
        Point2D point = new Point2D.Double(polygon.xpoints[i],
                polygon.ypoints[i]);
        rect.add(point);
    }
    return rect;
}

public static Polygon rectangleToPolygon(Rectangle2D rect) {
    Polygon poly = new Polygon();
    poly.addPoint((int) rect.getX(), (int) rect.getY());
    poly.addPoint((int) (rect.getX() + rect.getWidth()), (int) rect.getY());
    poly.addPoint((int) (rect.getX() + rect.getWidth()),
            (int) (rect.getY() + rect.getHeight()));
    poly.addPoint((int) rect.getX(), (int) (rect.getY() + rect.getHeight()));
    return poly;
}


public static class drawPolyAndRect extends JPanel {
    Polygon poly = new Polygon();

    public drawPolyAndRect() {
        poly.addPoint(0, 0);
        poly.addPoint(400, 40);
        poly.addPoint(400, 250);
        poly.addPoint(0, 400);

    }

    @Override
    @Transient
    public Dimension getPreferredSize() {
        return new Dimension(1000, 1000);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(Color.green);
        g2d.fill(poly);
        Composite c = AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                0.5f);
        g2d.setColor(Color.blue);
        g2d.setComposite(c);
        Rectangle2D polyToRect = polyToRect(poly);
        g2d.fill(polyToRect);

        // displace for drawing
        polyToRect.setFrame(polyToRect.getX() + 100,
                polyToRect.getY() + 100, polyToRect.getWidth(),
                polyToRect.getHeight());

        Polygon polyToRectToPoly = rectangleToPolygon(polyToRect);
        g2d.fill(polyToRectToPoly);

        g2d.dispose();
    }

}

public static void main(String[] args) {
    JFrame frame = new JFrame("Poly to rect");
    frame.getContentPane().add(new drawPolyAndRect());
    frame.pack();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}

本质上，这使用了将点添加到空rectangle2d的工作方式，它构建了包含所有四个点的最小矩形，拉伸了多边形。如果希望将返回的矩形作为多边形，请选中第二个静态方法。图片：

票数 1

Stack Overflow用户

发布于 2013-05-28 22:42:35

根据@lbalazscs answer的建议，使用PerspectiveTransform的基于JavaFX的解决方案。

Toggle Perspective在content.
Morph Perspective上打开和关闭透视效果，平滑地在透视转换和非透视转换内容之间进行动画转换。

import javafx.animation.*;
import javafx.application.*;
import javafx.beans.value.*;
import javafx.geometry.Pos;
import javafx.scene.*;
import javafx.scene.control.ToggleButton;
import javafx.scene.effect.PerspectiveTransform;
import javafx.scene.image.*;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.text.*;
import javafx.stage.Stage;
import javafx.util.Duration;

public class PerspectiveMovement extends Application {
  // perspective transformed group width and height.
  private final int W = 280;
  private final int H = 96;

  // upper right and lower right co-ordinates of perspective transformed group.
  private final int URY = 35;
  private final int LRY = 65;

  @Override public void start(Stage stage) {
    final PerspectiveTransform perspectiveTransform = createPerspectiveTransform();

    final Group group = new Group();
    group.setCache(true);
    setContent(group);

    final ToggleButton perspectiveToggle = createToggle(
      group, 
      perspectiveTransform
    );

    VBox layout = new VBox(10);
    layout.setAlignment(Pos.CENTER);
    layout.getChildren().setAll(
      perspectiveToggle,
      createMorph(perspectiveToggle, group, perspectiveTransform),
      group
    );
    layout.setStyle("-fx-padding: 10px; -fx-background-color: rgb(17, 20, 25);");

    stage.setScene(new Scene(layout));
    stage.show();
  }

  private void setContent(Group group) {
    Rectangle rect = new Rectangle(0, 5, W, 80);
    rect.setFill(Color.web("0x3b596d"));

    Text text = new Text();
    text.setX(4.0);
    text.setY(60.0);
    text.setText("A long time ago");
    text.setFill(Color.ALICEBLUE);
    text.setFont(Font.font(null, FontWeight.BOLD, 36));

    Image image = new Image(
      "http://icons.iconarchive.com/icons/danrabbit/elementary/96/Star-icon.png"
    );
    ImageView imageView = new ImageView(image);
    imageView.setX(50);

    group.getChildren().addAll(rect, imageView, text);
  }

  private PerspectiveTransform createPerspectiveTransform() {
    PerspectiveTransform perspectiveTransform = new PerspectiveTransform();

    perspectiveTransform.setUlx(0.0);
    perspectiveTransform.setUly(0.0);
    perspectiveTransform.setUrx(W);
    perspectiveTransform.setUry(URY);
    perspectiveTransform.setLrx(W);
    perspectiveTransform.setLry(LRY);
    perspectiveTransform.setLlx(0.0);
    perspectiveTransform.setLly(H);

    return perspectiveTransform;
  }

  private ToggleButton createToggle(final Group group, final PerspectiveTransform perspectiveTransform) {
    final ToggleButton toggle = new ToggleButton("Toggle Perspective");
    toggle.selectedProperty().addListener(new ChangeListener<Boolean>() {
      @Override public void changed(ObservableValue<? extends Boolean> observable, Boolean wasSelected, Boolean selected) {
        if (selected) {
          perspectiveTransform.setUry(URY);
          perspectiveTransform.setLry(LRY);
          group.setEffect(perspectiveTransform);
        } else {
          group.setEffect(null);
        }
      }
    });

    return toggle;
  }

  private ToggleButton createMorph(final ToggleButton perspectiveToggle, final Group group, final PerspectiveTransform perspectiveTransform) {
    final Timeline distorter = new Timeline(
      new KeyFrame(
        Duration.seconds(0), 
        new KeyValue(perspectiveTransform.uryProperty(), 0,  Interpolator.LINEAR),
        new KeyValue(perspectiveTransform.lryProperty(), H, Interpolator.LINEAR)
      ),
      new KeyFrame(
        Duration.seconds(3), 
        new KeyValue(perspectiveTransform.uryProperty(), URY, Interpolator.LINEAR),
        new KeyValue(perspectiveTransform.lryProperty(), LRY, Interpolator.LINEAR)
      )
    );

    final ToggleButton morphToggle = new ToggleButton("Morph Perspective");
    morphToggle.selectedProperty().addListener(new ChangeListener<Boolean>() {
      @Override public void changed(ObservableValue<? extends Boolean> observable, Boolean wasSelected, Boolean selected) {
        if (!perspectiveToggle.isSelected()) {
          perspectiveToggle.fire();
        }
        if (selected) {
          distorter.setRate(1);
          distorter.play();
        } else {
          distorter.setRate(-1);
          distorter.play();
        }
      }
    });

    return morphToggle;
  }
}