Java 中图片与二进制之间如何相互转换？
1、 下面是一个完整的代码示例。
- 指定文件路径转为二进制
- 将网络图片转为二进制
- base64 转为图片资源
package com.xxx.example.file;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.imageio.ImageIO;
import com.zxtc.syonline.support.common.StringUtil;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
public class ImageBioChangeUtil {
static BASE64Encoder encoder = new sun.misc.BASE64Encoder();
static BASE64Decoder decoder = new sun.misc.BASE64Decoder();
//从文件路径中获取图片转为二进制
public static String getImageBinary(String filePath){
if(StringUtil.isEmpty(filePath)) {
return null;
}
File f = new File(filePath); //这里gif动态图不可以，虽然在后面也能输出gif格式，但是却不是动图
BufferedImage bi;
try {
bi = ImageIO.read(f);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bi, "jpg", baos);
byte[] bytes = baos.toByteArray();
return encoder.encodeBuffer(bytes).trim();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
//从URl中获取图片转为二进制
public static String getImageBinaryFromUrl(String urlPath) throws Exception{
if(StringUtil.isEmpty(urlPath)) {
return "";
}
URL url=new URL(urlPath);
HttpURLConnection conn= (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(3000);//超时提示1秒=1000毫秒
InputStream inStream=conn.getInputStream();//获取输出流
byte[] data=readInputStream(inStream);
return encoder.encodeBuffer(data).trim();
}
//readInputStream方法
private static byte[] readInputStream(InputStream inStream) throws Exception{
ByteArrayOutputStream outStream=new ByteArrayOutputStream();
byte[] buffer=new byte[1024];//转换为二进制
int len=0;
while((len =inStream.read(buffer))!=-1){
outStream.write(buffer,0,len);
}
return outStream.toByteArray();
}
//将二进制转为图片
public static void base64StringToImage(String base64String,String outFilePath){
if(StringUtil.isNotEmpty(base64String)&&StringUtil.isNotEmpty(outFilePath)) {
try {
byte[] bytes1 = decoder.decodeBuffer(base64String);
ByteArrayInputStream bais = new ByteArrayInputStream(bytes1);
BufferedImage bi1 =ImageIO.read(bais);
File w2 = new File(outFilePath);//可以是jpg,png格式
if (!w2.exists()) { //文件不存在则创建文件，先创建目录
File dir = new File(w2.getParent());
dir.mkdirs();
w2.createNewFile(); // 创建新文件
}
ImageIO.write(bi1, "jpg", w2);//不管输出什么格式图片，此处不需改动
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
String imageBinary=null;
try {
imageBinary = getImageBinaryFromUrl("");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(imageBinary);
String outFilePath= "E://test//bio//zhh/aa.png";
base64StringToImage(imageBinary,outFilePath);
}
}2、如何判断 base64 图片的格式？
//判断图片base64字符串的文件格式
public static String checkImageBase64Format(String base64ImgData) {
byte[] b = Base64Util.decode(base64ImgData);
String type = "";
if (0x424D == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
type = "bmp";
} else if (0x8950 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
type = "png";
} else if (0xFFD8 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
type = "jpg";
}
return type;
}3、将网络图片转为 base64 字符串
/**
* 将网络路径图片转为base64的格式
* @param requestUrl 请求网络路径
* @throws Exception
*/
public static String getUrlImageToBase64(String requestUrl) throws Exception {
ByteArrayOutputStream data = new ByteArrayOutputStream();
try {
// 创建URL
URL url = new URL(requestUrl);
byte[] by = new byte[1024];
// 创建链接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5 * 1000);
InputStream is = conn.getInputStream();
// 将内容读取内存中
int len = -1;
while ((len = is.read(by)) != -1) {
data.write(by, 0, len);
}
// 关闭流
is.close();
} catch (IOException e) {
e.printStackTrace();
}
// 对字节数组Base64编码
Base64.Encoder encoder = Base64.getEncoder();
// return "data:image/" + photoType + ";base64," + encoder.encodeToString(data.toByteArray());
return encoder.encodeToString(data.toByteArray());
}4、将 base64 字符串转为图片输出
/**
* 将Base64编码的字符串转为文件输出
* @param base64String 字符串
* @param path 输出文件保存路径
* @param fileName 输出文件名称
* @return 是否转换成功
*/
public static boolean writeFileFromBase64(String base64String, String path, String fileName) {
if (base64String == null){
return false;
}
try {
byte[] b = Base64Util.decode(base64String);
File file = new File(path);
if(!file.exists()){
makeDir(file);
}
OutputStream out = new FileOutputStream(path + fileName);
out.write(b);
out.flush();
out.close();
return true;
}catch(Exception e){
e.printStackTrace();
return false;
}
}注：该方法的入参，base64 格式文件不得有 文件头部标识信息，否则会转换失败。所以这里我们需要自行判断是否包含有头部信息。
String urlImageToBase64 = "";//这里就是我们图片的base64字符串
if(urlImageToBase64.indexOf(",")>-1) {//包含头信息
System.out.println("包含头部信息");
urlImageToBase64 = urlImageToBase64.substring(urlImageToBase64.indexOf(",")+1);
}5、将文件转为 base64 字符串
/**
* 读入文件转换为Base64编码并返回
* @param filePath 文件路径
* @return base64 的文件
* @throws Exception
*/
public static String readAsBase64FromFile(String filePath) {
InputStream in = null;
byte[] data = null;
try {
in = new FileInputStream(fileName);
data = new byte[in.available()];
in.read(data);
in.close();
} catch(Exception e) {
e.printStackTrace();
return null;
}
return Base64Util.encode(data);
}上面用到了一个 Base64Util.java
package com.xxx.example.util;
public final class Base64Util {
static private final int BASELENGTH = 128;
static private final int LOOKUPLENGTH = 64;
static private final int TWENTYFOURBITGROUP = 24;
static private final int EIGHTBIT = 8;
static private final int SIXTEENBIT = 16;
static private final int FOURBYTE = 4;
static private final int SIGN = -128;
static private final char PAD = '=';
static private final boolean fDebug = false;
static final private byte[] base64Alphabet = new byte[BASELENGTH];
static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];
static {
for (int i = 0; i < BASELENGTH; ++i) {
base64Alphabet[i] = -1;
}
for (int i = 'Z'; i >= 'A'; i--) {
base64Alphabet[i] = (byte) (i - 'A');
}
for (int i = 'z'; i >= 'a'; i--) {
base64Alphabet[i] = (byte) (i - 'a' + 26);
}
for (int i = '9'; i >= '0'; i--) {
base64Alphabet[i] = (byte) (i - '0' + 52);
}
base64Alphabet['+'] = 62;
base64Alphabet['/'] = 63;
for (int i = 0; i <= 25; i++) {
lookUpBase64Alphabet[i] = (char) ('A' + i);
}
for (int i = 26, j = 0; i <= 51; i++, j++) {
lookUpBase64Alphabet[i] = (char) ('a' + j);
}
for (int i = 52, j = 0; i <= 61; i++, j++) {
lookUpBase64Alphabet[i] = (char) ('0' + j);
}
lookUpBase64Alphabet[62] = (char) '+';
lookUpBase64Alphabet[63] = (char) '/';
}
private static boolean isWhiteSpace(char octect) {
return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
}
private static boolean isPad(char octect) {
return (octect == PAD);
}
private static boolean isData(char octect) {
return (octect < BASELENGTH && base64Alphabet[octect] != -1);
}
/**
* Encodes hex octects into Base64
*
* @param binaryData
* Array containing binaryData
* @return Encoded Base64 array
*/
public static String encode(byte[] binaryData) {
if (binaryData == null) {
return null;
}
int lengthDataBits = binaryData.length * EIGHTBIT;
if (lengthDataBits == 0) {
return "";
}
int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
char encodedData[] = null;
encodedData = new char[numberQuartet * 4];
byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
int encodedIndex = 0;
int dataIndex = 0;
if (fDebug) {
System.out.println("number of triplets = " + numberTriplets);
}
for (int i = 0; i < numberTriplets; i++) {
b1 = binaryData[dataIndex++];
b2 = binaryData[dataIndex++];
b3 = binaryData[dataIndex++];
if (fDebug) {
System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
}
l = (byte) (b2 & 0x0f);
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
if (fDebug) {
System.out.println("val2 = " + val2);
System.out.println("k4 = " + (k << 4));
System.out.println("vak = " + (val2 | (k << 4)));
}
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
}
// form integral number of 6-bit groups
if (fewerThan24bits == EIGHTBIT) {
b1 = binaryData[dataIndex];
k = (byte) (b1 & 0x03);
if (fDebug) {
System.out.println("b1=" + b1);
System.out.println("b1<<2 = " + (b1 >> 2));
}
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
encodedData[encodedIndex++] = PAD;
encodedData[encodedIndex++] = PAD;
} else if (fewerThan24bits == SIXTEENBIT) {
b1 = binaryData[dataIndex];
b2 = binaryData[dataIndex + 1];
l = (byte) (b2 & 0x0f);
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
encodedData[encodedIndex++] = PAD;
}
return new String(encodedData);
}
/**
* Decodes Base64 data into octects
*
* @param encoded
* string containing Base64 data
* @return Array containind decoded data.
*/
public static byte[] decode(String encoded) {
if (encoded == null) {
return null;
}
char[] base64Data = encoded.toCharArray();
// remove white spaces
int len = removeWhiteSpace(base64Data);
if (len % FOURBYTE != 0) {
return null;// should be divisible by four
}
int numberQuadruple = (len / FOURBYTE);
if (numberQuadruple == 0) {
return new byte[0];
}
byte decodedData[] = null;
byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
char d1 = 0, d2 = 0, d3 = 0, d4 = 0;
int i = 0;
int encodedIndex = 0;
int dataIndex = 0;
decodedData = new byte[(numberQuadruple) * 3];
for (; i < numberQuadruple - 1; i++) {
if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
|| !isData((d3 = base64Data[dataIndex++])) || !isData((d4 = base64Data[dataIndex++]))) {
return null;
} // if found "no data" just return null
b1 = base64Alphabet[d1];
b2 = base64Alphabet[d2];
b3 = base64Alphabet[d3];
b4 = base64Alphabet[d4];
decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
}
if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
return null;// if found "no data" just return null
}
b1 = base64Alphabet[d1];
b2 = base64Alphabet[d2];
d3 = base64Data[dataIndex++];
d4 = base64Data[dataIndex++];
if (!isData((d3)) || !isData((d4))) {// Check if they are PAD characters
if (isPad(d3) && isPad(d4)) {
if ((b2 & 0xf) != 0)// last 4 bits should be zero
{
return null;
}
byte[] tmp = new byte[i * 3 + 1];
System.arraycopy(decodedData, 0, tmp, 0, i * 3);
tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
return tmp;
} else if (!isPad(d3) && isPad(d4)) {
b3 = base64Alphabet[d3];
if ((b3 & 0x3) != 0)// last 2 bits should be zero
{
return null;
}
byte[] tmp = new byte[i * 3 + 2];
System.arraycopy(decodedData, 0, tmp, 0, i * 3);
tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
return tmp;
} else {
return null;
}
} else { // No PAD e.g 3cQl
b3 = base64Alphabet[d3];
b4 = base64Alphabet[d4];
decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
}
return decodedData;
}
/**
* remove WhiteSpace from MIME containing encoded Base64 data.
*
* @param data
* the byte array of base64 data (with WS)
* @return the new length
*/
private static int removeWhiteSpace(char[] data) {
if (data == null) {
return 0;
}
// count characters that's not whitespace
int newSize = 0;
int len = data.length;
for (int i = 0; i < len; i++) {
if (!isWhiteSpace(data[i])) {
data[newSize++] = data[i];
}
}
return newSize;
}
}人生苦短，拒绝内卷。我是跟着飞哥学编程，一个一心向阳，向阳而生，努力向上生长的年轻人。加油兄弟们……
致力于实际工作场景中的避坑经验分享，无套路，纯干货。
爱飞哥，没毛病，飞哥带你上高速，冲冲冲……
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原始发表：2022-12-15，如有侵权请联系 cloudcommunity@tencent.com 删除
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