java - 从点创建 java.awt.geom.Area

Question

我正在尝试创建一个 java.awt.geom.Area(或任何使用 Shape 接口(interface)的对象)来描述一组创建复杂形状的点。这是一个例子:

我正在尝试创建一个 Area 对象(或多个 Area 对象)来描述黄色区域。我有一种获取黄色像素坐标的简单方法，但我不知道如何创建包含所有黄色点的 Area 对象(或多个 Area 对象)。

这个 stackoverflow 问题似乎非常相关 Create closed polygon from boundary points ) 但正在使用 Matlab。我认为其他人在这里问了一个非常相似的问题 ( Convert a list java.awt.geom.Point2D to a java.awt.geom.Area )，但答案中提供的链接已失效。

Answer 1

例如

import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.geom.Area;
import javax.imageio.ImageIO;
import java.io.File;
import java.net.URL;
import java.util.Date;
import javax.swing.*;

/* See also http://stackoverflow.com/q/7052422/418556 */
class ImageOutline {

    public static Area getOutline(
        BufferedImage image, Color color, boolean include, int tolerance) {

        Area area = new Area();
        for (int x=0; x<image.getWidth(); x++) {
            for (int y=0; y<image.getHeight(); y++) {
                Color pixel = new Color(image.getRGB(x,y));
                if (include) {
                    if (isIncluded(color, pixel, tolerance)) {
                        Rectangle r = new Rectangle(x,y,1,1);
                        area.add(new Area(r));
                    }
                } else {
                    if (!isIncluded(color, pixel, tolerance)) {
                        Rectangle r = new Rectangle(x,y,1,1);
                        area.add(new Area(r));
                    }
                }
            }
        }
        return area;
    }

    public static boolean isIncluded(
        Color target, Color pixel, int tolerance) {

        int rT = target.getRed();
        int gT = target.getGreen();
        int bT = target.getBlue();
        int rP = pixel.getRed();
        int gP = pixel.getGreen();
        int bP = pixel.getBlue();
        return(
            (rP-tolerance<=rT) && (rT<=rP+tolerance) &&
            (gP-tolerance<=gT) && (gT<=gP+tolerance) &&
            (bP-tolerance<=bT) && (bT<=bP+tolerance) );
    }

    public static BufferedImage drawOutline(int w, int h, Area area) {

        final BufferedImage result = new BufferedImage(
            w,
            h,
            BufferedImage.TYPE_INT_RGB);
        Graphics2D g = result.createGraphics();

        g.setColor(Color.white);
        g.fillRect(0,0,w,h);

        g.setClip(area);
        g.setColor(Color.red);
        g.fillRect(0,0,w,h);

        g.setClip(null);
        g.setStroke(new BasicStroke(1));
        g.setColor(Color.blue);
        g.draw(area);

        return result;
    }

    public static BufferedImage createAndWrite(
        BufferedImage image,
        Color color,
        boolean include,
        int tolerance,
        String name)
        throws Exception {

        int w = image.getWidth();
        int h = image.getHeight();

        System.out.println("Get Area: " + new Date() + " - " + name);
        Area area = getOutline(image, color, include, tolerance);
        System.out.println("Got Area: " + new Date() + " - " + name);

        final BufferedImage result = drawOutline(w,h,area);
        displayAndWriteImage(result, name);

        return result;
    }

    public static void displayAndWriteImage(
        BufferedImage image, String fileName) throws Exception {

        ImageIO.write(image, "png", new File(fileName));
        JOptionPane.showMessageDialog(null, new JLabel(new ImageIcon(image)));
    }

    public static void main(String[] args) throws Exception {
        URL url = new URL("http://i.stack.imgur.com/aGBuT.png");
        final BufferedImage outline = ImageIO.read(url);
        displayAndWriteImage(outline, "motorcycle-01.png");
        createAndWrite(
            outline, Color.white, false, 60, "YellowBlobOutline.png");
    }
}