VB.NET 图片和BASE64互转

• 2019 年 10 月 29 日
• 笔记

Base64是网络上最常见的用于传输8Bit字节码的编码方式之一，Base64就是一种基于64个可打印字符来表示二进制数据的方法。可查看RFC2045～RFC2049，上面有MIME的详细规范。

Base64编码是从二进制到字符的过程，可用于在HTTP环境下传递较长的标识信息。采用Base64编码具有不可读性，需要解码后才能阅读。

Base64由于以上优点被广泛应用于计算机的各个领域，然而由于输出内容中包括两个以上“符号类”字符（+, /, =)，不同的应用场景又分别研制了Base64的各种“变种”。为统一和规范化Base64的输出，Base62x被视为无符号化的改进版本。

图片转BASE64

    ''' <summary>      ''' 图片转BASE64      ''' </summary>      ''' <param name="IMG">要转换的图片</param>      ''' <returns></returns>      Function IMG_TO_BASE64(ByVal IMG As Image) As String          Try              If Not IsNothing(IMG) Then                  Dim MS As New IO.MemoryStream()                  Using BMP As New Bitmap(IMG)                      BMP.Save(MS, Imaging.ImageFormat.Jpeg)                      Dim BYT As Byte() = MS.GetBuffer()                      Dim Base64_Str As String = Convert.ToBase64String(BYT)                      Return Base64_Str                  End Using              Else                  Return "没有要转换的图片"              End If          Catch ex As Exception              Return ex.Message          End Try      End Function    

BASE64转图片

    ''' <summary>      ''' BASE64转图片      ''' </summary>      ''' <param name="BASE_STR">BASE64数据</param>      ''' <returns></returns>      Function BASE64_TO_IMG(ByVal BASE_STR As String) As Image          Try              Dim IMG As Image              If BASE_STR <> Nothing And Strings.Right(BASE_STR, 1) = "=" Then                  Dim BYT As Byte() = Convert.FromBase64String(BASE_STR)                  Dim MS As New IO.MemoryStream(BYT)                  IMG = Image.FromStream(MS)                  Return IMG              Else                  Return Nothing              End If          Catch ex As Exception              Return Nothing          End Try      End Function    

根据字符串计算图片转换后文件大小

    ''' <summary>      ''' 根据字符串计算txt文件大小      ''' </summary>      ''' <param name="picstr">字符串</param>      ''' <returns></returns>      Function PIC_LENG(ByVal picstr As String) As Double          Try              Dim bytes As Byte() = System.Text.Encoding.ASCII.GetBytes(picstr)              Dim Length As Integer = bytes.Length              Return Math.Round(Length / 1024 / 1024, 2)          Catch ex As Exception              Return 0          End Try      End Function