SWF to Video SDK can be used to convert Flash to image files in ASP.NET (using Visual Basic .NET or Visual C# as programming language).
Remember that you should have Administrator access to the web-server to install the SDK.

The sample VB and C# codes below show how to convert SWF to PNG image in ASP.NET using SWF To Video SDK.

ASP.NET (Visual Basic)

Imports System.IO

Imports BytescoutSWFToVideo

Public Partial Class _Default
    Inherits System.Web.UI.Page
    Protected Sub Page_Load(sender As Object, e As EventArgs)

        Dim inputSwfFile As String = Server.MapPath("Shapes.swf")

        ' Create an instance of SWFToVideo ActiveX object
        Dim converter As New SWFToVideo()

        ' Set debug log
        'converter.SetLogFile("log.txt");

        ' Register SWFToVideo
        converter.RegistrationName = "demo"

        converter.RegistrationKey = "demo"

        ' Enable trasparency - set BEFORE calling input SWF filename
        converter.RGBAMode = True

            ' Set input SWF file
            converter.InputSWFFileName = inputSwfFile
    
        ' Select the frame to extract (20th)
        converter.StartFrame = 20

        converter.StopFrame = 20

        ' Run conversion.
        ' Empty parameter means conversion to binary stream instead of file.
        converter.ConvertToPNG("")

        ' Display the extracted image:

        Response.Clear()
        ' Add content type header 
        Response.ContentType = "image/png"

        ' Set the content disposition 
        Response.AddHeader("Content-Disposition", "inline;filename=result.png")

        ' Write the image bytes into the Response output stream 

        Response.BinaryWrite(DirectCast(converter.BinaryImage, Byte()))

        Response.End()
    End Sub
End Class

ASP.NET (C#)

using System;
using System.IO;

using BytescoutSWFToVideo;

namespace SwfToPng
{
    public partial class _Default : System.Web.UI.Page
    {

        protected void Page_Load(object sender, EventArgs e)
        {

            String inputSwfFile = Server.MapPath("Shapes.swf");

            // Create an instance of SWFToVideo ActiveX object

            SWFToVideo converter = new SWFToVideo();

            // Set debug log
            //converter.SetLogFile("log.txt");

            // Register SWFToVideo
            converter.RegistrationName = "demo";
            converter.RegistrationKey = "demo";


            // Enable trasparency - set BEFORE setting SWF filename
            converter.RGBAMode = true;

            // set input SWF file

            converter.InputSWFFileName = inputSwfFile;


            // Select the frame to extract (20th)
            converter.StartFrame = 20;

            converter.StopFrame = 20;

            // Run conversion.
            // Empty parameter means conversion to binary stream instead of file.
            converter.ConvertToPNG("");

            // Display the extracted image:

            Response.Clear();
            // Add content type header 
            Response.ContentType = "image/png";

            // Set the content disposition 
            Response.AddHeader("Content-Disposition", "inline;filename=result.png");

            // Write the image bytes into the Response output stream 
            Response.BinaryWrite((byte[]) converter.BinaryImage);

            
            Response.End();
        }
    }
}
Sample SWF to image conversion:

 

Input SWF video – shapes.swf Output PNG image file – result.png