Checking if a rectangle intersects text

问题

I have a class called 'MapObject' which allows you to define what it is, what it does. I have recently added text to this, and it works fine however the collisions is a rectangle, which in some scenarios isn't horrible, however I would prefer to have a collision box matching the text (aka check if a 1x1 rectangle collides with the text but can still be inbetween letters)

I have tried the following:

GlyphVector vec = ob.font.createGlyphVector(new Canvas().getFontMetrics(ob.font).getFontRenderContext(), ob.text);
Shape textSh = vec.getOutline();
Area obSh = new Area(new Rectangle(x,y,o.width,o.height));
obSh.intersect(new Area(textSh));
boolean inter = !obSh.isEmpty();

However it just doesn't work, I imagine because of the location, however I don't know how to add a location into it. Thanks.

回答1:

One of the things you probably need to do is translate either the GlyphVector or Rectangle to the correct context.

What I mean is, the GlyphVector only represents the text at a origin point of 0x0, so if the text is displayed somewhere else on the screen, then you're not getting the correct representation.

Luckily, someone actually thought about this use case and provided some functionality to do it. See GlyphVector#getOutline(float, float) for more details.

You could then use it something like...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.font.FontRenderContext;
import java.awt.font.GlyphVector;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private List<Rectangle> boxes;
        private Map<Rectangle, Point> vectors;

        public TestPane() {
            boxes = new ArrayList<>(25);
            vectors = new HashMap<>(25);
            Random random = new Random();
            for (int index = 0; index < 10; index++) {
                int x = random.nextInt(400 - 10);
                int y = random.nextInt(400 - 10);

                Rectangle box = new Rectangle(x, y, 10, 10);
                boxes.add(box);

                int xDelta = random.nextBoolean() ? 1 : -1;
                int yDelta = random.nextBoolean() ? 1 : -1;

                vectors.put(box, new Point(xDelta, yDelta));
            }

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    for (Rectangle box : boxes) {
                        Point delta = vectors.get(box);

                        if (delta == null) {
                            int xDelta = random.nextBoolean() ? 1 : -1;
                            int yDelta = random.nextBoolean() ? 1 : -1;
                            delta = new Point(xDelta, yDelta);
                        }

                        int x = box.x + delta.x;
                        int y = box.y + delta.y;

                        if (x < 0) {
                            x = 0;
                            delta.x *= -1;
                        } else if (x + box.width > getWidth()) {
                            x = getWidth() - box.width;
                            delta.x *= -1;
                        }
                        if (y < 0) {
                            y = 0;
                            delta.y *= -1;
                        } else if (y + box.height > getHeight()) {
                            y = getHeight() - box.height;
                            delta.y *= -1;
                        }

                        box.setLocation(x, y);
                        vectors.put(box, delta);
                    }
                    repaint();
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 200);
        }

        protected Shape getTextShape() {
            Graphics2D g2d = (Graphics2D) getGraphics();
            if (g2d == null) {
                return null;
            }
            Font font = new Font("Arial", Font.BOLD, 48);
            g2d.setFont(font);

            FontRenderContext frc = g2d.getFontRenderContext();
            GlyphVector gv = font.createGlyphVector(frc, "Cats with hats");
            Rectangle2D box = gv.getVisualBounds();

            // Calclate the location of the text and offset the glyph shape...
            float x = (float) (getWidth() - box.getWidth()) / 2f;
            float y = (float) (((getHeight() - box.getHeight()) / 2f) + (-box.getY()));

            return gv.getOutline(x, y);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();

            Shape shape = getTextShape();

            g2d.setColor(Color.BLACK);
            g2d.fill(shape);
            g2d.setColor(Color.RED);
            g2d.draw(shape);

            for (Rectangle box : boxes) {
                g2d.setColor(Color.BLACK);
                if (shape.intersects(box)) {
                    g2d.setColor(Color.RED);
                }
                g2d.draw(box);
            }
        }

    }

}

来源：https://stackoverflow.com/questions/52748408/checking-if-a-rectangle-intersects-text