从MySQL数据库获取图像 - C＃

Question

我必须存储和恢复图像到/从MySQL数据库。为此，我使用此页上提供的说明：MySQL Forum，我可以通过下面的代码成功存储图片：

SaveIamge：

void SaveImage() 
    { 
     MemoryStream ms = new MemoryStream(); 
     pictureBox1.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); 
     cmd = new MySqlCommand("INSERT INTO " + tableName + " (Product, Manufacturer, Description, Price, Image) Values ('New_Product', 'New_Manufacturer', 'New_Description', '0', @Image)", conn); 
     cmd.Parameters.Add(new MySqlParameter("@Image", Convert.ToBase64String(ms.ToArray()))); 
     cmd.ExecuteNonQuery(); 
    } 

但我不能获取从数据库中的图像：我现在用下面的代码，请检查什么是错在这里：

GetThumbnail：

 void GetThumbnail() 
    { 
     string TN = tableNames[comboBox1.SelectedIndex]; 
     cmd = new MySqlCommand("SELECT Image FROM " + tableName + " WHERE Product = " + ProductTitle(), conn); 
     object imgObj = cmd.ExecuteScalar(); 
     byte[] b = Convert.FromBase64String(Convert.ToString(imgObj)); 
     MemoryStream ms = new MemoryStream(b); 
     pictureBox2.Image = Image.FromStream(ms); 
    } 

Answer 1

如何将图像存储到二进制字段？这将使比的Base64更有意义对其进行编码：

void SaveImage(byte[] image) 
{ 
    using (var conn = new MySqlConnection(ConnectionString)) 
    using (var cmd = conn.CreateCommand()) 
    { 
     cmd.CommandText = "INSERT INTO pictures (Product, Manufacturer, Description, Price, Image) VALUES ('New_Product', 'New_Manufacturer', 'New_Description', '0', ?Image)"; 
     cmd.Parameters.Add("?Image", image); 
     cmd.ExecuteNonQuery();  
    } 
} 

byte[] GetImage(string product) 
{ 
    using (var conn = new MySqlConnection(ConnectionString)) 
    using (var cmd = conn.CreateCommand()) 
    { 
     cmd.CommandText = "SELECT Image FROM pictures WHERE Product = ?product"; 
     cmd.Parameters.Add("?product", product); 
     using (var reader = cmd.ExecuteReader()) 
     { 
      if (!reader.Read()) 
      { 
       return null; 
      } 

      const int CHUNK_SIZE = 2 * 1024; 
      byte[] buffer = new byte[CHUNK_SIZE]; 
      long bytesRead; 
      long fieldOffset = 0; 
      using (var stream = new MemoryStream()) 
      { 
       while ((bytesRead = reader.GetBytes(reader.GetOrdinal("Image"), fieldOffset, buffer, 0, buffer.Length)) > 0) 
       { 
        stream.Write(buffer, 0, (int)bytesRead); 
        fieldOffset += bytesRead; 
       } 
       return stream.ToArray(); 
      } 
     } 
    } 
} 

然后：

using (var ms = new MemoryStream()) 
{ 
    pictureBox1.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); 
    SaveImage(ms.ToArray()); 
} 

，当你想要检索：

byte[] image = GetImage("New_Product"); 
MemoryStream stream = new MemoryStream(image); 
pictureBox2.Image = Image.FromStream(ms);