How to resize images using IHttpHandler?

Today we will see how to resize Images with IHttpHandler. Let’s put Image controls with three different sized images. Image will be same, but only sizes will be different.

<asp:Image ID="img" runat="server" ImageUrl="~/Desert.jpg?size=64" />
<asp:Image ID="Image1" runat="server" ImageUrl="~/Desert.jpg?size=164" />
<asp:Image ID="Image2" runat="server" ImageUrl="~/Desert.jpg?size=364" />

Here, you can see, I have passed sizes in querystring. Size=64 means I am requesting 64x64 size of that image. Now the next step is to make “ResizeImageHandler”. I am resizing image on the fly, means not storing anywhere. Just resizing image and throwing back to the response.
Note: requested image "Desert.jpg" must exist on your server, otherwise it will throw exception. I haven't handled exception because this is just example to understand IHttpHandler

Imports System.Drawing
Imports System.IO

Public Class ResizeImageHandler
    Implements IHttpHandler


    Public ReadOnly Property IsReusable As Boolean 
    Implements IHttpHandler.IsReusable
        Get
            Return True
        End Get
    End Property

    Public Sub ProcessRequest(context As HttpContext) 
    Implements IHttpHandler.ProcessRequest
         
        Dim req As HttpRequest = context.Request
        Dim res As HttpResponse = context.Response

        'Get the image file path '
        Dim path As String = req.PhysicalPath

        'Get the Image '
        Dim img As Image = Image.FromFile(path)

        'Image converter '
        Dim converter As New ImageConverter

        Dim s As Size
        If req.QueryString("size") IsNot Nothing Then

            'Get the size to Resize original image '
            Dim sz As String = req.QueryString("size")

            s = New Size(sz, sz)

            'Resize the original image to requested size '
            Dim bm As Bitmap = New Bitmap(img, s)

            'Convert to Image '
            Dim fImg As Image = bm

            'Write the Resized Image to browser '
            res.BinaryWrite(converter.ConvertTo(fImg, GetType(Byte())))
        Else

            'Write the original image '
            res.BinaryWrite(converter.ConvertTo(img, GetType(Byte())))
        End If
             
End Sub
 
End Class

Now, after creating class which implements IHttpHandler, we have to register it. I am using IIS 7 with Integrated Mode, so I have registered as below. There are different ways to register the Handler based on which IIS you are using and in which mode (classic/Integrated).
To know, which registration method you have to use, read this MSDN Article

<configuration>
  <system.webServer>
 <handlers>
    <add name="ResizeImageHandler" verb="GET"
           path="*.jpg"
           type="ResizeImageHandler"
           resourceType="Unspecified" />

 </handlers>
  </system.webServer>
</configuration>

Now it’s time to run the page with above Image server controls. After running that page, you will see following output.