從資料庫儲存和擷取影像是程式設計中的常見任務。雖然看起來很簡單，但如果程式碼未正確實現，則可能會出現問題。在本例中，使用者在將圖像儲存到資料庫並在 Picturebox 控制項中顯示圖像時遇到問題。
為了解決這個問題，讓我們檢查使用者的程式碼並識別潛在問題：
儲存到資料庫：
ImageStream = New System.IO.MemoryStream PbPicture.Image.Save(ImageStream, System.Drawing.Imaging.ImageFormat.Jpeg) ReDim rawdata(CInt(ImageStream.Length - 1))
程式碼無法使用正確的維度初始化原始資料。要正確儲存影像位元組，應重新調整大小以符合影像流的長度：
ReDim rawdata(CInt(ImageStream.Length))
從資料庫擷取：
Dim ad As New System.IO.MemoryStream(100000) Dim im As Image = Image.FromStream(ad) * "error occurs here" (see below)
錯誤出現此問題的原因是廣告記憶體流未正確定位或容量不足。以下程式碼修正了此問題：
ad.Position = 0 Dim im As Image = Image.FromStream(ad)
Dim filename As String = txtName.Text + ".jpg"
Dim FileSize As UInt32
conn.Close()
Dim mstream As New System.IO.MemoryStream()
PbPicture.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
Dim arrImage() As Byte = mstream.GetBuffer()
FileSize = mstream.Length
Dim sqlcmd As New MySqlCommand
Dim sql As String
mstream.Close()
sql = "insert into [your table] (picture, filename, filesize)
VALUES(@File, @FileName, @FileSize)"
Try
conn.Open()
With sqlcmd
.CommandText = sql
.Connection = conn
.Parameters.AddWithValue("@FileName", filename)
.Parameters.AddWithValue("@FileSize", FileSize)
.Parameters.AddWithValue("@File", arrImage)
.ExecuteNonQuery()
End With
Catch ex As Exception
MsgBox(ex.Message)
Finally
conn.Close()
End TryDim adapter As New MySqlDataAdapter
adapter.SelectCommand = Cmd
data = New DataTable
adapter = New MySqlDataAdapter("select picture from [yourtable]", conn)
commandbuild = New MySqlCommandBuilder(adapter)
adapter.Fill(data)
Dim lb() As Byte = data.Rows(0).Item("picture")
Dim lstr As New System.IO.MemoryStream(lb)
PbPicture.Image = Image.FromStream(lstr)
PbPicture.SizeMode = PictureBoxSizeMode.StretchImage
lstr.Close()以上是如何有效地從資料庫 Blob 儲存和檢索影像？的詳細內容。更多資訊請關注PHP中文網其他相關文章！
