我正在尝试使用带有CF的WinForm上的应用程序使用SQLite保存和加载图像。我找到了一种方法将图像保存到数据库中，但我不知道它是否正确，因为我找不到加载存储在数据库中的图像的方法。
我有一个代码可以将我的图像转换为Base64：
public void ImageToBase64(Image image, System.Drawing.Imaging.ImageFormat format){
using (MemoryStream ms = new MemoryStream()){
// Convert Image to byte[]
image.Save(ms, format);
byte[] imageBytes = ms.ToArray();
// Convert byte[] to Base64 String
string base64String = Convert.ToBase64String(imageBytes);
SaveImage(base64String);
}
}
这是我将图像保存到db：
的代码void SaveImage(string pic){
string query = "insert into Table (Photo) values (@pic);";
string conString = @" Data Source = \Program Files\Users.s3db ";
SQLiteConnection con = new SQLiteConnection(conString);
SQLiteCommand cmd = new SQLiteCommand(query, con);
cmd.Parameters.Add("@pic",DbType.String);
con.Open();
try{
cmd.ExecuteNonQuery();
}
catch (Exception exc1){
MessageBox.Show(exc1.Message);
}
con.Close();
}
我有一个与ImageToBase64相反的代码，但首先我需要从db加载图像。有没有想过呢？
编辑我正在尝试使用blob来保存图像，就像Charlie建议的那样。我试过这段代码：
Image photo = new Bitmap(@"\Photos\Image20120601_1.jpeg");
SaveImage(photo);
void SaveImage(Image pic){
string conString = @" Data Source = \Program Files\Users.s3db ";
SQLiteConnection con = new SQLiteConnection(conString);
SQLiteCommand cmd = con.CreateCommand();
cmd.CommandText = String.Format("INSERT INTO Table (Photo) VALUES (@0);");
SQLiteParameter param = new SQLiteParameter("@0", System.Data.DbType.Binary);
param.Value = pic;
cmd.Parameters.Add(param);
con.Open();
try{
cmd.ExecuteNonQuery();
}
catch (Exception exc1){
MessageBox.Show(exc1.Message);
}
con.Close();}
但是当我 ExcecuteNonQuery（）时，它会捕获 InvalidCastException 的错误。
有什么建议吗？
解决方案此代码将图像保存到数据库中，然后加载图像以在pictureBox中显示：
namespace ImagenSQLite
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Image photo = new Bitmap(@"\Photos\Image20120601_1.jpeg");
byte[] pic = ImageToByte(photo, System.Drawing.Imaging.ImageFormat.Jpeg);
SaveImage(pic);
LoadImage();
}
public byte[] ImageToByte(Image image, System.Drawing.Imaging.ImageFormat format){
using (MemoryStream ms = new MemoryStream())
{
// Convert Image to byte[]
image.Save(ms, format);
byte[] imageBytes = ms.ToArray();
return imageBytes;
}
}
//public Image Base64ToImage(string base64String)
public Image ByteToImage(byte[] imageBytes)
{
// Convert byte[] to Image
MemoryStream ms = new MemoryStream(imageBytes, 0, imageBytes.Length);
ms.Write(imageBytes, 0, imageBytes.Length);
Image image = new Bitmap(ms);
return image;
}
/***************** SQLite **************************/
void SaveImage(byte[] imagen){
string conStringDatosUsuarios = @" Data Source = \Program Files\GPS___CAM\Data\DatosUsuarios.s3db ";
SQLiteConnection con = new SQLiteConnection(conStringDatosUsuarios);
SQLiteCommand cmd = con.CreateCommand();
cmd.CommandText = String.Format("INSERT INTO Empleados (Foto) VALUES (@0);");
SQLiteParameter param = new SQLiteParameter("@0", System.Data.DbType.Binary);
param.Value = imagen;
cmd.Parameters.Add(param);
con.Open();
try
{
cmd.ExecuteNonQuery();
}
catch (Exception exc1)
{
MessageBox.Show(exc1.Message);
}
con.Close();
}
void LoadImage(){
string query = "SELECT Photo FROM Table WHERE ID='5';";
string conString = @" Data Source = \Program Files\Users.s3db ";
SQLiteConnection con = new SQLiteConnection(conString);
SQLiteCommand cmd = new SQLiteCommand(query, con);
con.Open();
try
{
IDataReader rdr = cmd.ExecuteReader();
try
{
while (rdr.Read())
{
byte[] a = (System.Byte[])rdr[0];
pictureBox1.Image = ByteToImage(a);
}
}
catch (Exception exc) { MessageBox.Show(exc.Message); }
}
catch (Exception ex) { MessageBox.Show(ex.Message); }
con.Close();
}
}
}
感谢您的帮助！
答案 0 :(得分：5)
要从数据库加载图像，可以使用SQL select语句来获取数据，就像使用任何其他类型的数据一样。 base64编码的图像作为字符串存储在SQLite数据库中。因此，您将它作为字符串检索，就像您在数据库中存储任何其他字符串（例如，您的名字）一样。
string LoadImage() {
string query = "select Photo from Table;";
string conString = @" Data Source = \Program Files\Users.s3db ";
SQLiteConnection con = new SQLiteConnection(conString);
SQLiteCommand cmd = new SQLiteCommand(query, con);
string base64EncodedImage = null;
con.Open();
try {
IDataReader reader = cmd.ExecuteReader();
reader.Read(); // advance the data reader to the first row
base64EncodedImage = (string) reader["Photo"];
reader.Close();
}
catch (Exception ex) {
MessageBox.Show(ex.Message);
}
con.Close();
return base64EncodedImage;
}
与保存代码一样，我加载图片的示例代码只使用保存在表格中的一张图片。要加载和保存多个映像，您需要在表中插入ID字段，然后在SQL where语句中使用select子句。
我不确定我个人会将图像存储为base64编码的字符串。图像的字符串表示将比二进制表示大得多。 SQLite supports the BLOB data type，所以我会考虑使用它。
答案 1 :(得分：0)
这是VB.net中的示例代码：
Imports System.IO
Imports System.Data.SQLite
Public Class Form1
'Image BLOB Functions:'
Private Function BlobToImage(ByVal blob)
Dim mStream As New System.IO.MemoryStream
Dim pData() As Byte = DirectCast(blob, Byte())
mStream.Write(pData, 0, Convert.ToInt32(pData.Length))
Dim bm As Bitmap = New Bitmap(mStream, False)
mStream.Dispose()
Return bm
End Function
'USE THIS FUNCTION TO CREATE A BLOB FROM AN IMAGE FILE'
Public Overloads Function ImageToBlob(ByVal id As String, ByVal filePath As String)
Dim fs As FileStream = New FileStream(filePath, FileMode.Open, FileAccess.Read)
Dim br As BinaryReader = New BinaryReader(fs)
Dim bm() As Byte = br.ReadBytes(fs.Length)
br.Close()
fs.Close()
'Create Parm'
Dim photo() As Byte = bm
Dim SQLparm As New SQLiteParameter("@image", photo)
SQLparm.DbType = DbType.Binary
SQLparm.Value = photo
Return SQLparm
End Function
'USE THIS FUNCTION TO CREATE A BLOB FROM AN IMAGE VARIABLE IN MEMORY'
Public Overloads Function ImageToBlob(ByVal id As String, ByVal image As Image)
Dim ms As New MemoryStream
image.Save(ms, System.Drawing.Imaging.ImageFormat.Png)
'Create Parm'
Dim photo() As Byte = ms.ToArray()
Dim SQLparm As New SQLiteParameter("@image", photo)
SQLparm.DbType = DbType.Binary
SQLparm.Value = photo
Return SQLparm
End Function
'USE THIS SUB TO CREATE A DB AND TABLE'
Private Sub btnCreateDB_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim SQLconnect As New SQLiteConnection()
Dim SQLcommand As New SQLiteCommand
SQLconnect.ConnectionString = "Data Source = " & Application.StartupPath & "\imgdb.sqlite3;"
SQLconnect.Open()
SQLcommand = SQLconnect.CreateCommand
'SQL Query to Create Table'
SQLcommand.CommandText = "CREATE TABLE foo(id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT, description TEXT, image BLOB);"
SQLcommand.ExecuteNonQuery()
SQLcommand.Dispose()
SQLconnect.Close()
End Sub
'USE THIS SUB TO INSERT IMAGE INTO SQLITE DB. IT GETS AN id INTEGER FROM
Textbox1'
Private Sub btnInsertImage_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim d As New OpenFileDialog
d.Filter = "image (*.png)|*.png|(*.jpg)|*.jpg|All files|*.*"
If d.ShowDialog() = DialogResult.OK Then
Dim myimage As Bitmap = Clipboard.GetImage()
Dim SQLconnect As New SQLite.SQLiteConnection()
Dim SQLcommand As New SQLiteCommand
SQLconnect.ConnectionString = "Data Source = " & Application.StartupPath & "\imgdb.sqlite3;"
SQLconnect.Open()
SQLcommand = SQLconnect.CreateCommand
'Insert Image, DO NOT single-quote @image'
SQLcommand.CommandText = "INSERT INTO foo (id,image) VALUES('" + TextBox1.Text + "', @image)"
'Define @image'
SQLcommand.Parameters.Add(ImageToBlob("@image", myimage))
SQLcommand.ExecuteNonQuery()
SQLcommand.Dispose()
SQLconnect.Close()
MessageBox.Show("Pic Inserted")
End If
End Sub
'USE THIS SUB TO GET THE BLOB FROM THE DB AND CONVERT IT BACK TO AN IMAGE'
Private Sub btnGetImageFromDB_Click(sender As Object, e As EventArgs) Handles Button3.Click
Dim SQLconnect As New SQLite.SQLiteConnection()
Dim SQLcommand As New SQLiteCommand
SQLconnect.ConnectionString = "Data Source = " & Application.StartupPath & "\imgdb.sqlite3;"
SQLconnect.Open()
SQLcommand = SQLconnect.CreateCommand
SQLcommand.CommandText = "SELECT image FROM foo WHERE id = '" + TextBox1.Text + "'"
Dim SQLreader As SQLiteDataReader = SQLcommand.ExecuteReader()
Dim myimage As Bitmap
While SQLreader.Read
myimage = BlobToImage(SQLreader("image"))
PictureBox1.Image = Nothing
PictureBox1.Image = myimage
End While
SQLcommand.Dispose()
SQLconnect.Close()
End Sub