将image图片转化为Base64字符串

最新推荐文章于 2025-05-16 13:52:50 发布

原创最新推荐文章于 2025-05-16 13:52:50 发布 · 3.1k 阅读

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本文介绍了如何将网络请求的图片和本地图片转化为Base64字符串。通过使用base64工具类，可以将图片数据转为byte数组，然后利用Base64Util.encode方法编码成字符串。对于网络图片，借助FileUtil.getImageFromNetByUrl方法；而对于本地图片，可以使用FileUtil.readFileByBytes方法读取文件后再进行编码。

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base64工具类：

/**
* Base64 工具类
*/
public class Base64Util {
private static final char last2byte = (char) Integer.parseInt("00000011", 2);
private static final char last4byte = (char) Integer.parseInt("00001111", 2);
private static final char last6byte = (char) Integer.parseInt("00111111", 2);
private static final char lead6byte = (char) Integer.parseInt("11111100", 2);
private static final char lead4byte = (char) Integer.parseInt("11110000", 2);
private static final char lead2byte = (char) Integer.parseInt("11000000", 2);
private static final char[] encodeTable = new char[]{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};

public Base64Util() {
}

public static String encode(byte[] from) {
StringBuilder to = new StringBuilder((int) ((double) from.length * 1.34D) + 3);
int num = 0;
char currentByte = 0;

int i;
for (i = 0; i < from.length; ++i) {
for (num %= 8; num < 8; num += 6) {
switch (num) {
case 0:
currentByte = (char) (from[i] & lead6byte);
currentByte = (char) (currentByte >>> 2);
case 1:
case 3:
case 5:
default:
break;
case 2:
currentByte = (char) (from[i] & last6byte);
break;
case 4:
currentByte = (char) (from[i] & last4byte);
currentByte = (char) (currentByte << 2);
if (i + 1 < from.length) {
currentByte = (char) (currentByte | (from[i + 1] & lead2byte) >>> 6);
}
break;
case 6:
currentByte = (char) (from[i] & last2byte);
currentByte = (char) (currentByte << 4);
if (i + 1 < from.length) {
currentByte = (char) (currentByte | (from[i + 1] & lead4byte) >>> 4);
}
}

to.append(encodeTable[currentByte]);
}
}

if (to.length() % 4 != 0) {
for (i = 4 - to.length() % 4; i > 0; --i) {
to.append("=");
}
}

return to.toString();
}
}

图片转byte工具类：

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

/**
* 文件读取工具类
*/
public class FileUtil {

/**
* 读取文件内容，作为字符串返回
*/
public static String readFileAsString(String filePath) throws IOException {
File file = new File(filePath);
if (!file.exists()) {
throw new FileNotFoundException(filePath);
}

if (file.length() > 1024 * 1024 * 1024) {
throw new IOException("File is too large");
}

StringBuilder sb = new StringBuilder((int) (file.length()));
// 创建字节输入流
FileInputStream fis = new FileInputStream(filePath);
// 创建一个长度为10240的Buffer
byte[] bbuf = new byte[10240];
// 用于保存实际读取的字节数
int hasRead = 0;
while ( (hasRead = fis.read(bbuf)) > 0 ) {
sb.append(new String(bbuf, 0, hasRead));
}
fis.close();
return sb.toString();
}

/**
* 根据文件路径读取byte[] 数组
*/
public static byte[] readFileByBytes(String filePath) throws IOException {
File file = new File(filePath);
if (!file.exists()) {
throw new FileNotFoundException(filePath);
} else {
ByteArrayOutputStream bos = new ByteArrayOutputStream((int) file.length());
BufferedInputStream in = null;

try {
in = new BufferedInputStream(new FileInputStream(file));
short bufSize = 1024;
byte[] buffer = new byte[bufSize];
int len1;
while (-1 != (len1 = in.read(buffer, 0, bufSize))) {
bos.write(buffer, 0, len1);
}

byte[] var7 = bos.toByteArray();
return var7;
} finally {
try {
if (in != null) {
in.close();
}
} catch (IOException var14) {
var14.printStackTrace();
}

bos.close();
}
}
}

/**
* 根据地址获得数据的字节流
* @param strUrl 网络连接地址
* @return
*/
public static byte[] getImageFromNetByUrl(String strUrl){
try {
URL url = new URL(strUrl);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5 * 1000);
InputStream inStream = conn.getInputStream();//通过输入流获取图片数据
byte[] btImg = readInputStream(inStream);//得到图片的二进制数据
return btImg;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 从输入流中获取数据
* @param inStream 输入流
* @return
* @throws Exception
*/
public static byte[] readInputStream(InputStream inStream) throws Exception{
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while( (len=inStream.read(buffer)) != -1 ){
outStream.write(buffer, 0, len);
}
inStream.close();
return outStream.toByteArray();
}

}

调用方法转化，返回base64字符串：

byte[] imgData = FileUtil.getImageFromNetByUrl(filePath);

String imgStr = Base64Util.encode(imgData);

上述是网络请求下的图片转base64

本地图片转base64的方法：

byte[] imgData = FileUtil.readFileByBytes(filePath);

String imgStr = Base64Util.encode(imgData);

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