利用Java实现在线图片URL转换为Base64以及反向解析成图片

import java.io.*;
import java.net.URL;
import java.util.Base64;

public class ImageUtils {

    /**
     * 在线图片 URL 转为 Base64 字符串
     * @param imageUrl 图片的在线地址
     * @return Base64 编码字符串
     * @throws IOException 网络异常或读取失败
     */
    public static String convertImageUrlToBase64(String imageUrl) throws IOException {
        URL url = new URL(imageUrl);
        try (InputStream is = url.openStream();
             ByteArrayOutputStream baos = new ByteArrayOutputStream()) {

            byte[] buffer = new byte[8192]; // 缓冲区
            int bytesRead;
            while ((bytesRead = is.read(buffer)) != -1) {
                baos.write(buffer, 0, bytesRead);
            }

            // 获取字节数组并进行 Base64 编码
            byte[] imageBytes = baos.toByteArray();
            return Base64.getEncoder().encodeToString(imageBytes);
        }
    }

    // 示例入口
    public static void main(String[] args) throws IOException {
        String url = "https://example.com/image.jpg";
        String base64 = convertImageUrlToBase64(url);
        System.out.println("Base64 编码结果：" + base64);
    }
}

import java.io.*;
import java.util.Base64;

public class Base64ToImage {

    /**
     * 将 Base64 编码字符串转为图片并保存本地
     * @param base64Str 图片的 Base64 字符串
     * @param outputPath 本地保存路径，如 "output.jpg"
     * @throws IOException 写入异常
     */
    public static void saveBase64ToImage(String base64Str, String outputPath) throws IOException {
        byte[] imageBytes = Base64.getDecoder().decode(base64Str);
        try (OutputStream os = new FileOutputStream(outputPath)) {
            os.write(imageBytes);
        }
    }

    // 示例入口
    public static void main(String[] args) throws IOException {
        String base64Str = "你的Base64编码";
        saveBase64ToImage(base64Str, "output.jpg");
        System.out.println("图片已保存至本地");
    }
}

import java.io.*;
import java.util.Base64;

public class Base64ToImage {

    /**
     * 从文本文件中读取 Base64，并保存为图片
     * @param base64FilePath 存储 Base64 的 .txt 文件路径
     * @param outputImagePath 输出图片路径
     * @throws IOException
     */
    public static void convertBase64FileToImage(String base64FilePath, String outputImagePath) throws IOException {
        // 读取 Base64 内容
        StringBuilder sb = new StringBuilder();
        try (BufferedReader reader = new BufferedReader(new FileReader(base64FilePath))) {
            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        }

        // 解码并写出图片
        byte[] imageBytes = Base64.getDecoder().decode(sb.toString());
        try (OutputStream os = new FileOutputStream(outputImagePath)) {
            os.write(imageBytes);
        }
    }

    public static void main(String[] args) throws IOException {
        String base64File = "base64_image.txt";
        String outputPath = "restored.jpg";
        convertBase64FileToImage(base64File, outputPath);
        System.out.println("图片还原成功！");
    }
}