C#实现Base64的编码解码

base64工作原理

Base64是MIME邮件中常用的编码方式之一。它的主要思想是将输入的字符串或数据编码成只含有{‘A‘-‘Z‘, ‘a‘-‘z‘, ‘0‘-‘9‘, ‘+‘, ‘/‘}这64个可打印字符的串，故称为“Base64”。

Base64编码的方法是，将输入数据流每次取6 bit，用此6 bit的值(0-63)作为索引去查表，输出相应字符。这样，每3个字节将编码为4个字符(3×8 → 4×6)；不满4个字符的以‘=‘填充。

//图片 转为    base64编码的文本
private void button1_Click(object sender, EventArgs e)
{
OpenFileDialog dlg = new OpenFileDialog();
dlg.Multiselect = true;
dlg.Title = "选择要转换的图片";
dlg.Filter = "Image files (*.jpg;*.bmp;*.gif;*.png)|*.jpg*.jpeg;*.gif;*.bmp|AllFiles (*.*)|*.*";
if (DialogResult.OK == dlg.ShowDialog())
{
for (int i = 0; i < dlg.FileNames.Length; i++)
{
ImgToBase64String(dlg.FileNames[i].ToString());
}
}
}
//图片 转为    base64编码的文本
private void ImgToBase64String(string Imagefilename)
{
try
{
Bitmap bmp = new Bitmap(Imagefilename);
this.pictureBox1.Image = bmp;
FileStream fs = new FileStream(Imagefilename + ".txt", FileMode.Create);
StreamWriter sw = new StreamWriter(fs);

MemoryStream ms = new MemoryStream();
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
byte[] arr = new byte[ms.Length];
ms.Position = 0;
ms.Read(arr, 0, (int)ms.Length);
ms.Close();
String strbaser64 = Convert.ToBase64String(arr);
sw.Write(strbaser64);

sw.Close();
fs.Close();
// MessageBox.Show("转换成功!");
}
catch (Exception ex)
{
MessageBox.Show("ImgToBase64String 转换失败\nException:" + ex.Message);
}
}

//base64编码的文本 转为    图片
private void button2_Click(object sender, EventArgs e)
{
OpenFileDialog dlg = new OpenFileDialog();
dlg.Multiselect = true;
dlg.Title = "选择要转换的base64编码的文本";
dlg.Filter = "txt files|*.txt";
if (DialogResult.OK == dlg.ShowDialog())
{
for (int i = 0; i < dlg.FileNames.Length; i++)
{
Base64StringToImage(dlg.FileNames[i].ToString());
}

}
}
//base64编码的文本 转为    图片
private void Base64StringToImage(string txtFileName)
{
try
{
FileStream ifs = new FileStream(txtFileName, FileMode.Open, FileAccess.Read);
StreamReader sr = new StreamReader(ifs);

String inputStr = sr.ReadToEnd();
byte[] arr = Convert.FromBase64String(inputStr);
MemoryStream ms = new MemoryStream(arr);
Bitmap bmp = new Bitmap(ms);

//bmp.Save(txtFileName + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
//bmp.Save(txtFileName + ".bmp", ImageFormat.Bmp);
//bmp.Save(txtFileName + ".gif", ImageFormat.Gif);
//bmp.Save(txtFileName + ".png", ImageFormat.Png);
ms.Close();
sr.Close();
ifs.Close();
this.pictureBox2.Image = bmp;
if (File.Exists(txtFileName))
{
File.Delete(txtFileName);
}
//MessageBox.Show("转换成功！");
}
catch (Exception ex)
{
MessageBox.Show("Base64StringToImage 转换失败\nException：" + ex.Message);
}
}