Through the Interface

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.Runtime;

using System;

using System.Drawing.Imaging;

using System.IO;

 

namespace ListApplications

{

  public static class Extensions

  {

    // Return the image format to use for a particular filename

 

    public static ImageFormat GetFormat(this string filename)

    {

      // If all else fails, let's create a PNG

      // (might also choose to throw an exception)

 

      var imf = ImageFormat.Png;

      if (filename.Contains("."))

      {

        // Get the filename's extension (what follows the last ".")

 

        string ext = filename.Substring(filename.LastIndexOf(".") + 1);

 

        // Get the first three characters of the extension

 

        if (ext.Length > 3)

          ext = ext.Substring(0, 3);

 

        // Choose the format based on the extension (in lowercase)

 

        switch (ext.ToLower())

        {

          case "bmp":

            imf = ImageFormat.Bmp;

            break;

          case "gif":

            imf = ImageFormat.Gif;

            break;

          case "jpg":

            imf = ImageFormat.Jpeg;

            break;

          case "tif":

            imf = ImageFormat.Tiff;

            break;

          case "wmf":

            imf = ImageFormat.Wmf;

            break;

          default:

            imf = ImageFormat.Png;

            break;

        }

      }

      return imf;

    }

  }

 

  public class Commands

  {

    [CommandMethod("CPI")]

    static public void CreatePreviewImage()

    {

      var doc = Application.DocumentManager.MdiActiveDocument;

      if (doc == null) return;

 

      var ed = doc.Editor;

 

      // Select the filename and type for our output image

 

      var pofo = new PromptSaveFileOptions("\nSelect image location");

 

      pofo.Filter =

        "Bitmap (*.bmp)|*.bmp|GIF (*.gif)|*.gif|JPEG (*.jpg)|*.jpg|" +

        "PNG (*.png)|*.png|TIFF (*.tif)|*.tif";

 

      // Set the default save location to be that of the current drawing

 

      string fn = doc.Database.Filename;

      if (fn.Contains("."))

      {

        int extIdx = fn.LastIndexOf(".");

        if (fn.Substring(extIdx + 1) != "dwt" && fn.Contains("\\"))

        {

          pofo.InitialDirectory = Path.GetDirectoryName(doc.Database.Filename);

        }

      }

 

      var pfnr = ed.GetFileNameForSave(pofo);

      if (pfnr.Status != PromptStatus.OK)

        return;

 

      var outFile = pfnr.StringResult;

 

      // Get the size of the document and capture the preview at that size

 

      var size = doc.Window.DeviceIndependentSize;

      using (

        var bmp =

          doc.CapturePreviewImage(

            Convert.ToUInt32(size.Width), Convert.ToUInt32(size.Height)

          )

      )

      {

        // Save the file with the format derived from the filename

 

        bmp.Save(outFile, outFile.GetFormat());

      }

    }

  }

}