System.Drawing/GDI+

Re: retrieve image from database then resize it before rendering on webpage

olalekex — Thu, 25 Jun 2009 05:51:45 GMT

Hi Benno74,

I made use of the tipps cmgray posted and it works

the 'outputSize' he mentioned is your own output size that you want the displayed image to have. for example you can replace the the line where 'outputSize is with 100. but first you have to declare the outputsize in int

    // Create a bitmap from the stream
    Bitmap bmp = new Bitmap(stream);

    Size new_size = new Size( );

   int outputSize=100;

    //resize based on the longer dimension
    if (bmp.Width > bmp.Height) {
     new_size.Width = outputSize;
     new_size.Height = (int)(((double)outputSize / (double)bmp.Width) * (double)bmp.Height);
    }
    else {
     new_size.Width = (int)(((double)outputSize / (double)bmp.Height) * (double)bmp.Width);
     new_size.Height = outputSize;
    }

if this answer helps you please mark as answer

olalekex

Re: retrieve image from database then resize it before rendering on webpage

Benno74 — Tue, 15 Jan 2008 01:08:36 GMT

Hi cmgray,

I've been looking at your code above for retrieving an image from a database and getting the image dimensions. You reference a variable called 'outputSize' . I was wondering where the value for this comes from?

Basically, I am successfully retrieving the image from the database and adding it to the Response.OutputStream stream, but cannot seem to get the image dimensions from the data, so I was looking at your code as it looks like it will achieve this. Everything else about it looks fine but just a bit stuck on the 'outputSize' value.

I know it was written a little while ago now, but any chance you - if you're still around (or someone else) - could give me some guidance on this?

Thanks in advance,

Ben

Re: retrieve image from database then resize it before rendering on webpage

cmgray — Sat, 25 Feb 2006 18:14:22 GMT

Here is some C# code that I use to do exactly that. I pull the image from an image field in a database and resize it memory, then put it out to the output stream.

public partial class ShowImage : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);

SqlCommand photoCommand = new SqlCommand("SELECT Image FROM Photos WHERE PhotoID = @PhotoID", connection);

photoCommand.Parameters.AddWithValue("@PhotoID", Request.QueryString["PhotoID"]);

try {
connection.Open( );

// Get bytes return from DB Command
byte[] b = (byte[])photoCommand.ExecuteScalar();

   if(b.Length > 0)
   {
    // Open a stream for the image and write the bytes into it
    System.IO.MemoryStream stream = new System.IO.MemoryStream(b, true);
    stream.Write(b, 0, b.Length);

    // Create a bitmap from the stream
    Bitmap bmp = new Bitmap(stream);

Size new_size = new Size( );

    //resize based on the longer dimension
    if (bmp.Width > bmp.Height) {
     new_size.Width = outputSize;
     new_size.Height = (int)(((double)outputSize / (double)bmp.Width) * (double)bmp.Height);
    }
    else {
     new_size.Width = (int)(((double)outputSize / (double)bmp.Height) * (double)bmp.Width);
     new_size.Height = outputSize;
    }
    Bitmap bitmap = new Bitmap(new_size.Width, new_size.Height, bmp.PixelFormat);
    Graphics new_g = Graphics.FromImage(bitmap);

    new_g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    new_g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    new_g.DrawImage(bmp, -1, -1, bitmap.Width + 1, bitmap.Height + 1);

bmp.Dispose( );

    //Draw the bitmapt to the outputstream
    bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
    bitmap.Dispose( );
    new_g.Dispose( );

    // Close the stream
    stream.Close( );
   }

   connection.Close( );
  }
  catch (Exception exc) {
   connection.Close( );
  }
    }
}

retrieve image from database then resize it before rendering on webpage

kenpatt — Mon, 30 Jan 2006 14:16:46 GMT

Here is my issue. I am trying to figure out the best way to pull an image from a database(the database holds the location of the image not the blob itself). Then while it is in memory resize the full sized image to a thumbnail.

I have the query that I want to use which is:

<%@ page explicit="true" language="vb" debug="true" %>
<%@ import namespace="system.data" %>
<%@ import namespace="MySql.Data.mysqlclient" %>

Sub page_load

If not ispostback then

'variables
Dim myConn as MySql.Data.MySqlClient.MySqlConnection
Dim sqlcmd as MySqlCommand
Dim dtrhomes as MySqldatareader

'database connection and query
myconn = new MySql.Data.MySqlClient.MySqlConnection ("Server=myserver;Database=mydbase;Uid=xxxx;Pwd=xxxx;")
myconn.open()
sqlcmd = new MysqlCommand("SELECT propertypic FROM waters ORDER BY RAND() LIMIT 1",myconn)
dtrhomes = sqlcmd.executereader()

'bind repeater
rpthomes.datasource = dtrhomes
rpthomes.databind()

dtrhomes.close()
myconn.close()
end if
end sub
</script>

<asp:repeater ID="rpthomes" Runat="server">
<itemTemplate>
<img src='<%# container.dataItem("propertypic") %>' >
</itemTemplate>
</asp:repeater>

Now comes the hard part how do I marry the above with this:

<@ page content type="image/jpeg" %>
<@ import namespace="system.drawing" %>
<@ import namespace="system.drawing.imaging" %>

Sub page_load
Dim objBitmap As Bitmap
Dim objGraphics As Graphics

'create bitmap
objBitmap = new Bitmap(120,120)

objGraphics = Graphics.FromImage( objBitmap )

'display bitmap

objBitmap.save( response.outputstram, imageformat.jpeg )

End sub
</script>

As you see I want to create an image that is 120x120 and that the image location is stored in the propertypic field in a database.

Thanks for all the help

Ken.