base64 java将jpg文件转换为字节字符串，然后再次转换回jpg

Question

我不明白我做错了什么。同样的xyz。jpg文件我被编码成字节字符串。现在，当我试图从相同的字节字符串转换jpg文件时，我得到了一个错误

破例

java.lang.IllegalArgumentException: Length of Base64 encoded input string is not a multiple of 4.
    at let.application.Base64Coder.decode(Base64Coder.java:95)
    at let.application.Base64Coder.decode(Base64Coder.java:92)
    at let.application.Base64Coder.decode(Base64Coder.java:89)
    at let.application.TestImage.main(TestImage.java:29)

我的主要申请

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;

import javax.imageio.ImageIO;

import org.apache.commons.io.FileUtils;

import sun.misc.BASE64Encoder;


public class TestImage {

    public static void main(String[] args) {

        try {
            String filePath = "c:\\AFS\\FBUMP_IMAGE.jpg";

            //Encode
            byte[] fileContent = FileUtils.readFileToByteArray(new File(filePath));
            BASE64Encoder base64encoder = new BASE64Encoder();
            String encodedString = base64encoder.encode(fileContent);  // GALC way
            System.out.println(encodedString);
            
            // Decode
            byte[] bytearray = Base64Coder.decode(encodedString);
            BufferedImage imag;
            imag = ImageIO.read(new ByteArrayInputStream(bytearray));
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            System.out.println(imag);
            ImageIO.write(imag, "png", baos);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

请注意：Base64编码器。java已经存在了，我必须“用它来解码”

/**
 *
 * @author
 *    Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland, www.source-code.biz
 */
public class Base64Coder {

    //The line separator string of the operating system.
    private static final String systemLineSeparator = System.getProperty("line.separator");

    //Mapping table from 6-bit nibbles to Base64 characters.
    private static final char[] map1 = new char[64];
    static {
        int i=0;
        for (char c='A'; c<='Z'; c++) map1[i++] = c;
        for (char c='a'; c<='z'; c++) map1[i++] = c;
        for (char c='0'; c<='9'; c++) map1[i++] = c;
        map1[i++] = '+'; map1[i++] = '/'; }

    //Mapping table from Base64 characters to 6-bit nibbles.
    private static final byte[] map2 = new byte[128];
    static {
        for (int i=0; i<map2.length; i++) map2[i] = -1;
        for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; }

    public static String encodeString (String s) {
        return new String(encode(s.getBytes())); }

    public static String encodeLines (byte[] in) {
        return encodeLines(in, 0, in.length, 76, systemLineSeparator); }

    
    public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) {
        int blockLen = (lineLen*3) / 4;
        if (blockLen <= 0) throw new IllegalArgumentException();
        int lines = (iLen+blockLen-1) / blockLen;
        int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length();
        StringBuilder buf = new StringBuilder(bufLen);
        int ip = 0;
        while (ip < iLen) {
            int l = Math.min(iLen-ip, blockLen);
            buf.append(encode(in, iOff+ip, l));
            buf.append(lineSeparator);
            ip += l; }
        return buf.toString(); }

    public static char[] encode (byte[] in) {
        return encode(in, 0, in.length); }

    public static char[] encode (byte[] in, int iLen) {
        return encode(in, 0, iLen); }

    public static char[] encode (byte[] in, int iOff, int iLen) {
        int oDataLen = (iLen*4+2)/3;       // output length without padding
        int oLen = ((iLen+2)/3)*4;         // output length including padding
        char[] out = new char[oLen];
        int ip = iOff;
        int iEnd = iOff + iLen;
        int op = 0;
        while (ip < iEnd) {
            int i0 = in[ip++] & 0xff;
            int i1 = ip < iEnd ? in[ip++] & 0xff : 0;
            int i2 = ip < iEnd ? in[ip++] & 0xff : 0;
            int o0 = i0 >>> 2;
            int o1 = ((i0 &   3) << 4) | (i1 >>> 4);
            int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
            int o3 = i2 & 0x3F;
            out[op++] = map1[o0];
            out[op++] = map1[o1];
            out[op] = op < oDataLen ? map1[o2] : '='; op++;
            out[op] = op < oDataLen ? map1[o3] : '='; op++; }
        return out; }

    public static String decodeString (String s) {
        return new String(decode(s)); }

    public static byte[] decodeLines (String s) {
        char[] buf = new char[s.length()];
        int p = 0;
        for (int ip = 0; ip < s.length(); ip++) {
            char c = s.charAt(ip);
            if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
                buf[p++] = c; }
        return decode(buf, 0, p); }

    public static byte[] decode (String s) {
        return decode(s.toCharArray()); }

    public static byte[] decode (char[] in) {
        return decode(in, 0, in.length); }

    public static byte[] decode (char[] in, int iOff, int iLen) {
        if (iLen%4 != 0) throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4.");
        while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--;
        int oLen = (iLen*3) / 4;
        byte[] out = new byte[oLen];
        int ip = iOff;
        int iEnd = iOff + iLen;
        int op = 0;
        while (ip < iEnd) {
            int i0 = in[ip++];
            int i1 = in[ip++];
            int i2 = ip < iEnd ? in[ip++] : 'A';
            int i3 = ip < iEnd ? in[ip++] : 'A';
            if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
                throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
            int b0 = map2[i0];
            int b1 = map2[i1];
            int b2 = map2[i2];
            int b3 = map2[i3];
            if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
                throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
            int o0 = ( b0       <<2) | (b1>>>4);
            int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
            int o2 = ((b2 &   3)<<6) |  b3;
            out[op++] = (byte)o0;
            if (op<oLen) out[op++] = (byte)o1;
            if (op<oLen) out[op++] = (byte)o2; }
        return out; }

    //Dummy constructor.
    private Base64Coder() {}

} // end class Base64Coder

Answer 1

下面是一个工作示例

1. 用java.util.Base64替换BASE64Encoder

import org.apache.commons.io.FileUtils;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.util.Base64;

public class TestImage {

    public static void main(String[] args) {

        try {
            String filePath = "IMG_20200711.jpg";

            //Encode
            byte[] fileContent = FileUtils.readFileToByteArray(new File(filePath));

//            BASE64Encoder base64encoder = new BASE64Encoder();
            String encodedString = Base64.getEncoder().encodeToString(fileContent);  // GALC way
            System.out.println(encodedString);
            
            // Decode
            byte[] bytearray = Base64.getDecoder().decode(encodedString);
            BufferedImage imag;
            imag = ImageIO.read(new ByteArrayInputStream(bytearray));
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            System.out.println("output buffer: " + imag);
            String fileExtension = "png";
            ImageIO.write(imag, fileExtension, baos);
            File file = new File("IMG_20200711_111422_1." + fileExtension);
            ImageIO.write(imag, fileExtension, file); // recreates same image with different name

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出：

//truncated since its big string and each image has different values

/9j/4AAQSkZJRgABAQAAAQABAAD .......  8lQDedSshTqGUuopVmBzSmxPlYVB//Z

output buffer: BufferedImage@6166e06f: type = 5 ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace@8b96fde transparency = 1 has alpha = false isAlphaPre = false ByteInterleavedRaster: width = 4032 height = 3024 #numDataElements 3 dataOff[0] = 2

Ref