Question

我的应用程序要求从SD卡中选择图像文件，所选图像应转换或编码为base64二进制格式字符串。我可以从SD卡获取图像文件并获取其路径和名称，但无法转换它以base64二进制格式字符串。

谢谢， Sumith.M.P

Answer 1

将图片转换为base64字符串：

Bitmap bm = BitmapFactory.decodeFile("/path/to/image.jpg");
ByteArrayOutputStream baos = new ByteArrayOutputStream();  
bm.compress(Bitmap.CompressFormat.JPEG, 100, baos);   
byte[]  = baos.toByteArray(); 

String encodedImage = Base64.encodeToString(b, Base64.DEFAULT);

Answer 2

早于8的Android版本没有内置Base64。在这种情况下，您可以使用此类。

public class Base64 {
   private static final char[] S_BASE64CHAR = {
       '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', '+', '/'
   };
   private static final char S_BASE64PAD = '=';
   private static final byte[] S_DECODETABLE = new byte[128];
   static {
       for (int i = 0;  i < S_DECODETABLE.length;  i ++)
           S_DECODETABLE[i] = Byte.MAX_VALUE;  // 127
       for (int i = 0;  i < S_BASE64CHAR.length;  i ++) // 0 to 63
           S_DECODETABLE[S_BASE64CHAR[i]] = (byte)i;
   }

   private static int decode0(char[] ibuf, byte[] obuf, int wp) throws Exception {
       int outlen = 3;
       if (ibuf[3] == S_BASE64PAD)  outlen = 2;
       if (ibuf[2] == S_BASE64PAD)  outlen = 1;
       int b0 = S_DECODETABLE[ibuf[0]];
       int b1 = S_DECODETABLE[ibuf[1]];
       int b2 = S_DECODETABLE[ibuf[2]];
       int b3 = S_DECODETABLE[ibuf[3]];
       switch (outlen) {
       case 1:
           obuf[wp] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
           return 1;
       case 2:
           obuf[wp++] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
           obuf[wp] = (byte)(b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
           return 2;
       case 3:
           obuf[wp++] = (byte)(b0 << 2 & 0xfc | b1 >> 4 & 0x3);
           obuf[wp++] = (byte)(b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
           obuf[wp] = (byte)(b2 << 6 & 0xc0 | b3 & 0x3f);
           return 3;
       default:
           throw new Exception("internalError00");
       }
   }

   /**
    *
    */
   public static byte[] decode(char[] data, int off, int len) throws Exception {
       char[] ibuf = new char[4];
       int ibufcount = 0;
       byte[] obuf = new byte[len/4*3+3];
       int obufcount = 0;
       for (int i = off;  i < off+len;  i ++) {
           char ch = data[i];
           if (ch == S_BASE64PAD
               || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
               ibuf[ibufcount++] = ch;
               if (ibufcount == ibuf.length) {
                   ibufcount = 0;
                   obufcount += decode0(ibuf, obuf, obufcount);
               }
           }
       }
       if (obufcount == obuf.length)
           return obuf;
       byte[] ret = new byte[obufcount];
       System.arraycopy(obuf, 0, ret, 0, obufcount);
       return ret;
   }

   /**
    *
    */
   public static byte[] decode(String data) throws Exception {
       char[] ibuf = new char[4];
       int ibufcount = 0;
       byte[] obuf = new byte[data.length()/4*3+3];
       int obufcount = 0;
       for (int i = 0;  i < data.length();  i ++) {
           char ch = data.charAt(i);
           if (ch == S_BASE64PAD
               || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
               ibuf[ibufcount++] = ch;
               if (ibufcount == ibuf.length) {
                   ibufcount = 0;
                   obufcount += decode0(ibuf, obuf, obufcount);
               }
           }
       }
       if (obufcount == obuf.length)
           return obuf;
       byte[] ret = new byte[obufcount];
       System.arraycopy(obuf, 0, ret, 0, obufcount);
       return ret;
   }


   /**
    * Returns base64 representation of specified byte array.
    */
   public static String encode(byte[] data) {
       return encode(data, 0, data.length);
   }

   /**
    * Returns base64 representation of specified byte array.
    */
   public static String encode(byte[] data, int off, int len) {
       if (len <= 0)  return "";
       char[] out = new char[len/3*4+4];
       int rindex = off;
       int windex = 0;
       int rest = len-off;
       while (rest >= 3) {
           int i = ((data[rindex]&0xff)<<16)
                   +((data[rindex+1]&0xff)<<8)
                   +(data[rindex+2]&0xff);
           out[windex++] = S_BASE64CHAR[i>>18];
           out[windex++] = S_BASE64CHAR[(i>>12)&0x3f];
           out[windex++] = S_BASE64CHAR[(i>>6)&0x3f];
           out[windex++] = S_BASE64CHAR[i&0x3f];
           rindex += 3;
           rest -= 3;
       }
       if (rest == 1) {
           int i = data[rindex]&0xff;
           out[windex++] = S_BASE64CHAR[i>>2];
           out[windex++] = S_BASE64CHAR[(i<<4)&0x3f];
           out[windex++] = S_BASE64PAD;
           out[windex++] = S_BASE64PAD;
       } else if (rest == 2) {
           int i = ((data[rindex]&0xff)<<8)+(data[rindex+1]&0xff);
           out[windex++] = S_BASE64CHAR[i>>10];
           out[windex++] = S_BASE64CHAR[(i>>4)&0x3f];
           out[windex++] = S_BASE64CHAR[(i<<2)&0x3f];
           out[windex++] = S_BASE64PAD;
       }
       return new String(out, 0, windex);
   }

}

在android中将图像文件编码为64 Base Binary Format

2 个答案: