java - java中的文本转图像

Question

我正在尝试将 .txt 文件中的一行文本转换为 java 中的 .jpeg 图像。我编写了以下代码:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;
import java.io.*;
import java.util.*;

public class ProjTry extends JFrame
{
    static BufferedImage img;
    static Graphics g;
    static String s;

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.drawImage(img,0,0,this);
    }

    /* public*/ ProjTry(String fname) //throws Exception
    {
        BufferedReader br = null;
        try
            {
                br = new BufferedReader(new FileReader(fname));
                //EDIT
                while ((s=br.readLine()) != null)
                    {
                        System.out.println(s);
                    }

            }
        catch (IOException e)
            {
                e.printStackTrace();
            }
        finally
            {
                try
                    {
                        if (br != null)br.close();
                    }
                catch (IOException ex)
                    {
                        ex.printStackTrace();
                    }
            }

    }

    public static void main(String args[])throws Exception
    {
        ProjTry tx=new ProjTry("E:\\Java\\file.txt");
        JFrame j=new JFrame("Demo");
        g=img.getGraphics();
        g.drawString(s,0,0);
        try
            {
                FileOutputStream fos=new FileOutputStream("E:\\Java\\t2img.jpg");
                ImageIO.writeImage(img,"jpg",fos);
                fos.close();
            }
        catch(Exception ex)
            {
                ex.printStackTrace();
            }
    }
}

这里我的文件名为“file.txt”。然而编译器不断显示 2 个错误。我该怎么办？

错误::

第 17 行:找不到符号

     super(.)paintComponent(g);

符号:方法paintComponent(Graphics)

第 79 行:找不到符号

     ImageIO(.)writeImage(img,"jpg",fos);

符号:方法writeImage(BufferedImage,String,FileOutputStream)

位置:ImageIO 类

Answer 1

错误消息准确地告诉您出了什么问题 - 相信它们并进行检查，您将能够自行解决这些问题和类似问题。

public class ProjTry extends JFrame
{
    static BufferedImage img;
    static Graphics g;
    static String s;

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.drawImage(img,0,0,this);
    }

The method paintComponent(Graphics) is undefined for the type JFrame

JFrame API 将确认这是真的，当您看到此错误和类似错误时，应该查找 API。看起来您已经复制了 JPanel 的绘制代码并将其放入 JFrame 中，并且您不应该这样做。在扩展 JPanel 的类内部进行绘制，就像在您借用该类的代码中所做的那样，然后将该 JPanel 放入 JFrame 中。

此外，始终在您的重写方法(您认为重写父类方法的方法)前面加上@Override注释。如果您这样做:

@Override
public void paintComponent(Graphics g) {
   // etc...

编译器会警告您，您实际上并没有重写 super 方法。

站点注释:paintComponent 方法应该是 protected 而不是 public

<小时/>

ImageIO.writeImage(img,"jpg",fos);

The method writeImage(BufferedImage, String, FileOutputStream) is undefined for the type ImageIO

ImageIO API 将再次确认这是真的，并且事实上此类没有 writeImage 方法。请改用 ImageIO.write(...) 方法，*正如 API 将向您展示的那样。或者更一般地说:仅使用 API 规定可用的方法。

例如——没有写入图像文件:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.Scanner;    
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

@SuppressWarnings("serial")
public class DrawOnImg extends JPanel {
    public static final String IMG_PATH = "https://upload.wikimedia.org/"
            + "wikipedia/commons/thumb/c/c9/Thomas_Hicks_-_Leopold_Grozelier_-_"
            + "Presidential_Candidate_Abraham_Lincoln_1860.jpg/"
            + "456px-Thomas_Hicks_-_Leopold_Grozelier_-_Presidential_Candidate_"
            + "Abraham_Lincoln_1860.jpg";
    public static final String TXT_PATH = "http://history.eserver.org/"
            + "gettysburg-address.txt";
    public static final String NEW_LINE = System.getProperty("line.separator");
    private BufferedImage backgroundImg = null;

    public DrawOnImg(BufferedImage img, String text) {
        backgroundImg = img;

        JTextArea textArea = new JTextArea(text);
        textArea.setOpaque(false);
        setLayout(new GridBagLayout());
        add(textArea);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (backgroundImg != null) {
            g.drawImage(backgroundImg, 0, 0, this);
        }
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet() || backgroundImg == null) {
            return super.getPreferredSize();
        }
        int w = backgroundImg.getWidth();
        int h = backgroundImg.getHeight();
        return new Dimension(w, h);
    }

    private static void createAndShowGui(BufferedImage img, String text) {
        DrawOnImg mainPanel = new DrawOnImg(img, text);

        JFrame frame = new JFrame("DrawOnImg");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        Scanner scanner = null;
        try {
            URL txtUrl = new URL(TXT_PATH);
            scanner = new Scanner(txtUrl.openStream());
            final String text = readText(scanner);

            URL imgUrl = new URL(IMG_PATH);
            final BufferedImage img = ImageIO.read(imgUrl);
            SwingUtilities.invokeLater(() -> createAndShowGui(img, text));
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(-1);
        } finally {
            if (scanner != null) {
                scanner.close();
            }
        }

    }

    private static String readText(Scanner scanner) {
        StringBuilder sb = new StringBuilder();
        boolean save = false;
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine().trim();
            if (line.startsWith("Four score")) {
                save = true;
            } 
            if (line.startsWith("-----")) {
                save = false;
            }
            if (save && !line.isEmpty()) {
                sb.append(line);
                sb.append(NEW_LINE);
            }
        }
        return sb.toString();
    }
}

哪些输出: