C#BASE64 encoding [transcoding]__

I. Coding rules for BASE64

The idea of BASE64 encoding is to encode the data using 64 basic ASCII characters. It splits the data that needs to be encoded into a byte array. A group of 3 bytes. Arrange the 24-bit data in order, then divide the 24-bit data into 4 groups, that is, 6 bits per group. Then fill a byte with two 0 in front of each group's top digit. This encodes a 3-byte-A-group of data back into 4 bytes. When the number of bytes of data to be encoded is not an integral multiple of 3, that is, the last group is not 3 bytes when grouped. This is populated with 1 to 2 0 bytes in the last group. and add 1 to 2 "=" At the end after the final encoding is complete.

Example: BASE64 encoding of ABC will be performed:

1, first take the corresponding ASCII value of ABC. (A) B (C) (67);
2, then take the binary value A (01000001) B (01000010) C (01000011);
3, then the three bytes of the binary code to connect (010000010100001001000011);
4, then 6-bit units into 4 blocks, and at the highest level of two 0 after the formation of 4 bytes encoded values, (00010000) (00010100) (00001001) (00000011), where the blue part of the real data;
5. Convert these four bytes of data into 10 (16) (20) (9) (3);
6. Finally, according to the 64 basic character tables given by BASE64, find the corresponding ASCII code character (Q) (U) (J) (D), where the value is actually the index of the data in the character table.

Note: BASE64 character chart: abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789+/

Two. Decoding rules

The decoding process is to restore 4 bytes to 3 bytes and then rearrange the byte array into data according to different data forms.

Three. Implementation in C #

Coding:

byte [] bytes = Encoding.Default.GetBytes ("character to convert");
String str = convert.tobase64string (bytes);

Decoding

byte [] Outputb = convert.frombase64string (str);
String orgstr = Encoding.Default.GetString (OUTPUTB);

Base64 encoding and decoding of C # pictures

BASE64 encoding of the picture:

System.IO.MemoryStream m = new System.IO.MemoryStream ();
System.Drawing.Bitmap bp = new System.Drawing.Bitmap (@ "C:\Demo. GIF ");
Bp. Save (M, System.Drawing.Imaging.ImageFormat.Gif);
byte []b = M.getbuffer ();
String base64string = convert.tobase64string (b);

Base64 string decoding:

Byte [] bt  =  convert.frombase64string (base64string);
system.io.memorystream stream  =  New  system.io.memorystream (BT);
bitmap bitmap  =  new  bitmap (stream);
picturebox1.image  =  bitmap;