Thumbnail.OCX for .NET 64 bit

Anonymous — Fri, 14 Feb 2014 14:31:07 GMT

Back in the day I used the Thumbnail.ocx to display a preview of a dwg file in a form.

I need to upgrade (re-write) an old VB6 program to the 21st centry using VB.NET and was wondering if there is a new version or a subsitute that I could use, maybe something from TrueView?

Any help is greatly appreciated.

Ray C.

Re: Thumbnail.OCX for .NET 64 bit

norman.yuan — Fri, 14 Feb 2014 16:45:52 GMT

You can find .NET code that retrieves thumbnail bitmap image from *.dwg file here:

http://www.theswamp.org/index.php?topic=30985.msg470910#msg470910

http://www.theswamp.org/index.php?topic=45598.msg507524#msg507524

Re: Thumbnail.OCX for .NET 64 bit

Anonymous — Fri, 14 Feb 2014 19:09:31 GMT

Looks great.
This is a bit over my head but when I create my class it is throwing an error on the line
fs.CopyTo(ms, imageHeaderStart)

Re: Thumbnail.OCX for .NET 64 bit

Anonymous — Fri, 14 Feb 2014 19:12:02 GMT

Sorry about that hit the worng key and submitted the post to quick.

As I was syaing it is posting an development error that
'CopyTo' is not a member of 'System.IO.FileStream'
Have you had a chance to use that code?

Thanks for the help

Ray C.

Re: Thumbnail.OCX for .NET 64 bit

norman.yuan — Fri, 14 Feb 2014 19:58:37 GMT

FileStream.CopyTo() method is only available since .NET4.0. Since all my Acad development targets Acad2012 or later, I stoped using .NET2/3.x.

Yes, I used the code with minor change, worked OK with AutoCAD 2012's drawing. Here is the static class I use:

using System;
using System.Drawing;
using System.IO;

namespace DrawingThumbnail
{
    /// <summary>
    /// This code is originally from http://www.theswamp.org:
    /// http://www.theswamp.org/index.php?topic=30985.msg470910#msg470910
    /// http://www.theswamp.org/index.php?topic=45598.msg507524#msg507524
    /// Minor code change has be made
    /// </summary>
    public static class DwgThumbnail
    {
        public static Image GetBitmapFromDwgFile(string dwgFile)
        {
            if (!File.Exists(dwgFile))
            {
                throw new FileNotFoundException("Cannot find file: \"" + dwgFile + "\"");
            }

            if (!Path.GetExtension(dwgFile).ToUpper().EndsWith("DWG"))
            {
                throw new ArgumentException("Wrong file type: not a *.DWG file.");
            }

            Image img = null;

            using (FileStream fs = new FileStream(dwgFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                using (BinaryReader br = new BinaryReader(fs))
                {
                    fs.Seek(0xd, SeekOrigin.Begin);
                    fs.Seek(0x14 + br.ReadInt32(), SeekOrigin.Begin);
                    byte bytCnt = br.ReadByte();
                    if (bytCnt <= 1)
                    {
                        return null;
                    }

                    int imageHeaderStart = 0;
                    int imageHeaderSize = 0;
                    byte imageCode = 0;
                    for (short i = 1; i <= bytCnt; i++)
                    {
                        imageCode = br.ReadByte();
                        imageHeaderStart = br.ReadInt32();
                        imageHeaderSize = br.ReadInt32();
                        
                        if (imageCode == 2)
                        {
                            //-----------------------------------------
                            // BMP Preview (2012 file format)
                            //-----------------------------------------

                            // BITMAPINFOHEADER (40 bytes)
                            br.ReadBytes(0xe);

                            //biSize, biWidth, biHeight, biPlanes
                            ushort biBitCount = br.ReadUInt16();
                            br.ReadBytes(4);

                            //biCompression
                            uint biSizeImage = br.ReadUInt32();

                            //br.ReadBytes(0x10); //biXPelsPerMeter, biYPelsPerMeter, biClrUsed, biClrImportant
                            fs.Seek(imageHeaderStart, SeekOrigin.Begin);
                            byte[] bitmapBuffer = br.ReadBytes(imageHeaderSize);
                            uint colorTableSize = 
                                Convert.ToUInt32(Math.Truncate((biBitCount < 9) ? 4 * Math.Pow(2, biBitCount) : 0));
                            using (MemoryStream ms = new MemoryStream())
                            {
                                using (BinaryWriter bw = new BinaryWriter(ms))
                                {
                                    bw.Write(Convert.ToUInt16(0x4d42));
                                    bw.Write(54u + colorTableSize + biSizeImage);
                                    bw.Write(new ushort());
                                    bw.Write(new ushort());
                                    bw.Write(54u + colorTableSize);
                                    bw.Write(bitmapBuffer);
                                    img = new Bitmap(ms);
                                }
                            }
                            
                        }       
                        else if (imageCode == 6)
                        {
                            //-------------------------------------------
                            // PNG Preview (2013 file format)
                            //-------------------------------------------
                            fs.Seek(imageHeaderStart, SeekOrigin.Begin);
                            using (MemoryStream ms = new MemoryStream())
                            {
                                fs.CopyTo(ms, imageHeaderStart);
                                img = Image.FromStream(ms);
                            }
                        }
                        else if (imageCode == 3)
                        {
                            //return null;
                        }
                    }
                }
            }

            return img;
        }
    }
}

HTH

Re: Thumbnail.OCX for .NET 64 bit

Anonymous — Fri, 14 Feb 2014 20:01:56 GMT

That's what I concluded. I'm using VS2008, does not support .NET 4.0.
Time for an upgrade.
Thanks for all your help.

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