Question

我正在尝试检索存储在oracle blob中的图像，并将其放在新的System.Drawing.Image实例中。我知道我可以将流写入磁盘上的temp.bmp文件并从那里读取它，但这对我来说不够。如何将blob对象直接转换为图像？

Answer 1

假设：

您正在使用Microsoft客户端（System.Data.OracleClient）。
您有一个正确的OracleConnection实例（connection）。
您已准备好OracleCommand（command，基于SELECT my_blob FROM my_table WHERE id=xx）。

这应该是这样的：

using (OracleDataReader odr=command.ExecuteReader())
{
    reader.Read();

    if (!dr.IsDBNull(0))
        using (Stream s=(Stream)dr.GetOracleValue(0))
            using (Image image=Image.FromStream(s))
                return Copy(image);
}

复制是

public static Image Copy(Image original)
{
    Image ret=new Bitmap(original.Width, original.Height);
    using (Graphics g=Graphics.FromImage(ret))
    {
        g.DrawImageUnscaled(original, 0, 0);
        g.Save();
    }

    return ret;
}

请参阅my blog post和/或KB 814675了解为何需要复制。

Answer 2

我知道这会使用sql，但它应该与您的需求类似

Dim cn As SqlConnection = Nothing
        Dim cmd As SqlCommand = Nothing
        Dim da As SqlDataAdapter = Nothing
        Dim ms As MemoryStream = Nothing
        Dim dsImage As Data.DataSet = Nothing
        Dim myBytes() As Byte = Nothing
        Dim imgJPG As System.Drawing.Image = Nothing
        Dim msOut As MemoryStream = Nothing

        Try
            cn = New SqlConnection(ConnectionStrings("conImageDB").ToString)
            cmd = New SqlCommand(AppSettings("sprocGetImage").ToString, cn)
            cmd.CommandType = Data.CommandType.StoredProcedure

            cmd.Parameters.AddWithValue("@dmhiRowno", irowno)

            da = New SqlDataAdapter(cmd)

            dsImage = New Data.DataSet
            da.Fill(dsImage, "image")

            If dsImage.Tables(0).Rows.Count = 0 Then
                Throw New Exception("No results returned for rowno")
            End If
            myBytes = dsImage.Tables(0).Rows(0)("Frontimage")

            ms = New MemoryStream
            ms.Write(myBytes, 0, myBytes.Length)

            imgJPG = System.Drawing.Image.FromStream(ms)

            'Export to JPG Stream
            msOut = New MemoryStream
            imgJPG.Save(msOut, System.Drawing.Imaging.ImageFormat.Jpeg)
            imgJPG.Dispose()
            imgJPG = Nothing
            ms.Close()
            sFrontImage = Convert.ToBase64String(msOut.ToArray())

            dsImage = New Data.DataSet
            da.Fill(dsImage, "image")
            myBytes = dsImage.Tables(0).Rows(0)("Backimage")

            ms = New MemoryStream
            ms.Write(myBytes, 0, myBytes.Length)

            imgJPG = System.Drawing.Image.FromStream(ms)
            sBackImage = Convert.ToBase64String(ms.ToArray)

        Catch ex As System.IO.IOException ' : An I/O error occurs.
            Throw ex
        Catch ex As System.ArgumentNullException ': buffer is null.
            Throw ex
        Catch ex As System.NotSupportedException ': The stream does not support writing. For additional information see System.IO.Stream.CanWrite.-or- The current position is closer than count bytes to the end of the stream, and the capacity cannot be modified.
            Throw ex
        Catch ex As System.ArgumentOutOfRangeException ': offset or count are negative.
            Throw ex
        Catch ex As System.ObjectDisposedException ' : The current stream instance is closed.
            Throw ex
        Catch ex As System.ArgumentException
            Throw ex
        Catch ex As System.Runtime.InteropServices.ExternalException ': The image was saved with the wrong image format
            Throw ex
        Catch ex As Exception
            Throw ex
        Finally
            If cn IsNot Nothing Then
                cn.Close()
                cn.Dispose()
                cn = Nothing
            End If

            If cmd IsNot Nothing Then
                cmd.Dispose()
                cmd = Nothing
            End If

            If da IsNot Nothing Then
                da.Dispose()
                da = Nothing
            End If

            If ms IsNot Nothing Then
                ms.Dispose()
                ms = Nothing
            End If

            If msOut IsNot Nothing Then
                msOut.Close()
                msOut.Dispose()
                msOut = Nothing
            End If

            If dsImage IsNot Nothing Then
                dsImage.Dispose()
                dsImage = Nothing
            End If

            If myBytes IsNot Nothing Then
                myBytes = Nothing
            End If

            If imgJPG IsNot Nothing Then
                imgJPG.Dispose()
                imgJPG = Nothing
            End If

        End Try

此代码为前图像拉回tiff包装的jpeg，因此代码与后图像略有不同。

如何将存储为oracle blob的图像存入Image对象

2 个答案: