How can I convert image url to system.drawing.image

You could use WebClient class to download image and then MemoryStream to read it:

C#

WebClient wc = new WebClient();
byte[] bytes = wc.DownloadData("http://localhost/image.gif");
MemoryStream ms = new MemoryStream(bytes);
System.Drawing.Image img = System.Drawing.Image.FromStream(ms);

VB

Dim wc As New WebClient()
Dim bytes As Byte() = wc.DownloadData("http://localhost/image.gif")
Dim ms As New MemoryStream(bytes)
Dim img As System.Drawing.Image = System.Drawing.Image.FromStream(ms)