Unable to create Thumbnail Image for AutoCAD

[Anonymous]

Hi,

I am using below method for getting Bitmap object from autocad file.

This method is working fine for AutoCAD 2012 application

But same is not working in AutoCAD 2013 application

Please help me on this.

Regards,

Raman

publicBitmap GetAutoCADBitmap(string strFile, bool boolRetainBackColor)

        {

Bitmap bmp = newBitmap(1, 1, PixelFormat.Format8bppIndexed);

byte bytCnt = 0;

byte[] bytBMPBuff = null;

int lngImgLoc = 0;

BinaryReader br = null;

int lngCurLoc = 0;

int lngY = 0;

int lngX = 0;

int lngColor = 0;

int lngCnt = 0;

short intCnt = 0;

IMGREC udtRec = default(IMGREC);

RGBQUAD[] udtColors = null;

RGBQUAD udtColor = default(RGBQUAD);

BITMAPINFOHEADER udtHeader = default(BITMAPINFOHEADER);

short intRed = 0;

short intGreen = 0;

short intBlue = 0;

if (File.Exists(strFile))

            {

using (FileStream fs = newFileStream(strFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))

                {

                    br =

newBinaryReader(fs);

                    fs.Seek(13,

SeekOrigin.Begin);

                    lngImgLoc = br.ReadInt32();

                    fs.Seek(lngImgLoc + 17,

SeekOrigin.Begin);

                    lngCurLoc = lngImgLoc + 17;

                    fs.Seek(lngCurLoc + 3,

SeekOrigin.Begin);

                    bytCnt = br.ReadByte();

if (bytCnt > 1)

                    {

for (intCnt = 0; intCnt <= bytCnt - 1; intCnt++)

                        {

                            udtRec.bytType = br.ReadByte();

                            udtRec.lngStart = br.ReadInt32();

                            udtRec.lngLen = br.ReadInt32();

if (udtRec.bytType == 2)

                            {

                                fs.Seek(udtRec.lngStart,

SeekOrigin.Begin);

                                udtHeader.biSize = br.ReadInt32();

udtHeader.biWidth = br.ReadInt32();

udtHeader.biHeight = br.ReadInt32();

                                udtHeader.biPlanes = br.ReadInt16();

                                udtHeader.biBitCount = br.ReadInt16();

                                udtHeader.biCompression = br.ReadInt32();

                                udtHeader.biSizeImage = br.ReadInt32();

                                udtHeader.biXPelsPerMeter = br.ReadInt32();

                                udtHeader.biYPelsPerMeter = br.ReadInt32();

                                udtHeader.biClrUsed = br.ReadInt32();

                                udtHeader.biClrImportant = br.ReadInt32();

                                bytBMPBuff =

newbyte[udtRec.lngLen + 1];

if (udtHeader.biBitCount == 8)

                                {

                                    udtColors =

newRGBQUAD[256];

for (int count = 0; count <= 255; count++)

                                    {

                                        udtColors[count].rgbBlue = br.ReadByte();

udtColors[count].rgbGreen = br.ReadByte();

                                        udtColors[count].rgbRed = br.ReadByte();

                                        udtColors[count].rgbReserved = br.ReadByte();

                                    }

                                    fs.Seek(udtRec.lngStart - 1,

SeekOrigin.Begin);

for (int count = 0; count <= udtRec.lngLen; count++)

                                    {

                                        bytBMPBuff[count] = br.ReadByte();

                                    }

                                    bmp =

newBitmap(udtHeader.biWidth, udtHeader.biHeight);

                                    lngCnt = 0;

for (lngY = 1; lngY <= udtHeader.biHeight; lngY++)

                                    {

for (lngX = udtHeader.biWidth; lngX >= 1; lngX += -1)

                                        {

                                            lngColor = bytBMPBuff[bytBMPBuff.GetUpperBound(0) - lngCnt];

                                            udtColor = udtColors[lngColor];

                                            intRed =

Convert.ToInt16(udtColor.rgbRed);

                                            intGreen =

Convert.ToInt16(udtColor.rgbGreen);

                                            intBlue =

Convert.ToInt16(udtColor.rgbBlue);

                                            lngColor =

ColorTranslator.ToOle(Color.FromArgb(intRed, intGreen, intBlue));

if (boolRetainBackColor == false)

                                            {

if (lngColor == ColorTranslator.ToOle(Color.Black))

                                                {

                                                    lngColor =

ColorTranslator.ToOle(Color.White);

                                                }

else

                                                {

if (lngColor == ColorTranslator.ToOle(Color.White))

                                                    {

                                                        lngColor =

ColorTranslator.ToOle(Color.Black);

                                                    }

                                                }

                                            }

                                            bmp.SetPixel(lngX - 1, lngY - 1,

ColorTranslator.FromOle(lngColor));

                                            lngCnt += 1;

                                        }

                                    }

                                }

                            }

else

                            {

if (udtRec.bytType == 3)

returnnull;

                            }

                        }

                    }

else

returnnull;

                }

            }

return bmp;

        }

[Balaji_Ram]

Hi Raman,

In 2013 Dwg file format, the thumbnail image is a PNG.

It is a BMP prior to 2013.

This discussion @ theswamp can help with your code :

http://www.theswamp.org/index.php?topic=30985.15

[Anonymous]

does this mean we need to c# convert bmp to png image, so that we can creat a thumnail for cad. it will be easy to me if so. i already download an amazing image app.

[Balaji_Ram]

You do not need any conversion utility.

The thumbnail image is now stored in PNG format in the drawing and so while retieving it you will find a different image code.

Refer to the sample code in the link that I provided earlier. There is an additional check for imageCode equals 6.

Hope this explains.