Recently I had to generate thumbs from AutoCad DWG files. I found out that a BMP preview is stored within the file and created a DWGThumbnailer that can be registered on your lib. Thought you would like to have a copy. Of course if you find any room for improvement on the code, feel free to do it.
Best regards,
Rodrigo Deppe
public void generateThumbnail(File input, File output) throws IOException, de.uni_siegen.wineme.come_in.thumbnailer.ThumbnailerException {
//GENERATE FROM EXISTING BITMAP IN DWG
byte[] outputByte = new byte[4096];
FileInputStream fis = new FileInputStream(input);
fis.skip(0x0D);
fis.read(outputByte, 0, 4);
int PosSentinel = (((outputByte[3])&0xFF)*256*256*256)+(((outputByte[2])&0xFF)*256*256)+(((outputByte[1])&0xFF)*256)+((outputByte[0])&0xFF);
fis.skip(PosSentinel-0x0D-4+30);
outputByte[1]=0;
fis.read(outputByte, 0, 1);
int TypePreview = ((outputByte[0])&0xFF);
if (TypePreview==2) {
fis.read(outputByte, 0, 4);
int PosBMP = (((outputByte[3])&0xFF)*256*256*256)+(((outputByte[2])&0xFF)*256*256)+(((outputByte[1])&0xFF)*256)+((outputByte[0])&0xFF);
fis.read(outputByte, 0, 4);
int LenBMP = (((outputByte[3])&0xFF)*256*256*256)+(((outputByte[2])&0xFF)*256*256)+(((outputByte[1])&0xFF)*256)+((outputByte[0])&0xFF);
fis.skip(PosBMP-(PosSentinel+30)-1-4-4+14);
fis.read(outputByte, 0, 2);
int biBitCount = (((outputByte[1])&0xFF)*256)+((outputByte[0])&0xFF);
fis.skip(-16);
int bisSize=0;
int bfSize = 0;
if (biBitCount<9)
bfSize = 54 + 4 * ((int) (Math.pow(2,biBitCount))) + LenBMP ;
else bfSize = 54 + LenBMP ;
//WORD "BM"
outputByte[0]=0x42;outputByte[1]=0x4D;
//DWORD bfSize
outputByte[2]=(byte)(bfSize&0xff);outputByte[3]=(byte)(bfSize>>8&0xff);
outputByte[4]=(byte)(bfSize>>16&0xff);outputByte[5]=(byte)(bfSize>>>24);
//WORD bfReserved1
outputByte[6]=0x00;outputByte[7]=0x00;
//WORD bfReserved2
outputByte[8]=0x00;outputByte[9]=0x00;
//DWORD bfOffBits
outputByte[10]=0x36;outputByte[11]=0x04;outputByte[12]=0x00;outputByte[13]=0x00;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
baos.write(outputByte,0,14);
while((LenBMP>0) && ((bisSize=fis.read(outputByte, 0, (LenBMP>4096?4096:LenBMP))) != -1)) {
baos.write(outputByte, 0, bisSize);
LenBMP-=bisSize;
}
ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
try {
BufferedImage originalImage = ImageIO.read(bais);
float scaleWidth = ((float) this.thumbWidth) / originalImage.getWidth();
float scaleHeight = ((float) this.thumbHeight) / originalImage.getHeight();
int newWidth = this.thumbWidth;
int newHeight = this.thumbHeight;
//PRESERVE ASPECT RATIO
if (scaleWidth<scaleHeight)
newHeight=Math.round(newHeight*scaleWidth);
else newWidth=Math.round(newWidth*scaleHeight);
BufferedImage newImage = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);
Graphics g = newImage.createGraphics();
g.drawImage(originalImage, 0, 0, newWidth, newHeight, null);
g.dispose();
ImageIO.write(newImage,"jpg",output);
} catch (Exception e) {
//STILL TO DO: support 32bit bitmap rescaling
bais.reset();
FileOutputStream fos = new FileOutputStream(output);
while ((bisSize=bais.read(outputByte, 0, 4096)) != -1)
fos.write(outputByte, 0, bisSize);
fos.close();
}
}
fis.close();
}
public String[] getAcceptedMIMETypes() {
String dwgMIME = "image/x-dwg" ;
Collection dwgMIMEColl = new ArrayList();
dwgMIMEColl.add(dwgMIME) ;
return (String[]) dwgMIMEColl.toArray(new String[dwgMIMEColl.size()]);
}
Hello,
I've been using this lib for quite a while now. Congratulations on the good job done.
Recently I had to generate thumbs from AutoCad DWG files. I found out that a BMP preview is stored within the file and created a DWGThumbnailer that can be registered on your lib. Thought you would like to have a copy. Of course if you find any room for improvement on the code, feel free to do it.
Best regards,
Rodrigo Deppe
Here is the code:
public class DWGThumbnailer extends DummyThumbnailer {
}