Anyone tried the DCT and IDCT code?

Hi,
I was linked to the following link which provides a DCT and IDCT code:
http://forum.java.sun.com/thread.jsp?forum=426&thread=482368&start=15&range=15&hilite=false&q=
However, when I tried to run it, the resulting (IDCT-ed) array seems to be very different from the origianl array.
For example, the first array element is 1.0, but after the DCT-IDCT process, it becomes 259.99997. And many other become 0.0 or -ve numbers.
I would like to ask if anyone has tried to use that? Does it work....? If not, is there any way to correct it? Or are there any other links to DCT-IDCT with Java source code? I really need it.....
Thanks.

Hi there,
I guess I have made a mistake in using the methods.
The code CAN IDCT the FDCT data it creates. Just take care of which float array in the IDCT method is the output array (the 3 argument).
Sorry about the misunderstand of the code and any confusion caused.

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Hello everyone,
Applying the dct (discrete cosine transformation) and then the idct to a PlanarImage should return the original picture before the transformation, shouldn't it?
implementing it the following way:
ParameterBlock pb = null;
PlanarImage image = null;
image = JAI.create("fileload", "d:\\rainbow.jpg");
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Hi sprossi,
Thanks for your reply.
I think I'm facing the problem you faced previously about the JAI would "reset" the image dimension to powers of 2 upon DCT and IDCT.... and as far as I know is to use Rectangle class to "chop" it back...
The JAI is a bit too difficult for me to use.... meanwhile I'm looking for codes that directly perfrom DCT and IDCT without using JAI. I've seen the code in the replies, but it's for 8X8, and I would like to to work on a 1-D double array which I get from:
bufferedImage.getData().getPixels(0, 0, bufImage.getWidth(), bufImage.getHeight(),(double[])null);
have you seen any DCT and IDCT that can work on 1-D array?
Also, I'm looking for a way to transform the watermarked 1-D double array back to a BufferedImage. There is a link telling how this is done on a 2-D double array.
http://archives.java.sun.com/cgi-bin/wa?A2=ind9907&L=jai-interest&P=R1637
I've tried to modify it for 1-D array, but it didn't success. An ArrayIndexOutOfBoundException is raised when I tried to do a setData()... here is the code I wrote, may be you can have a look on that....
public BufferedImage double2BufImage(int width, int height, int numBands, double[] imgData) {
          * Step 1:
          * create a SampleModel to accomdate the double data
          SampleModel sampleModel = RasterFactory.createBandedSampleModel(DataBuffer.TYPE_DOUBLE, width, height, numBands);
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          * Step 2:
          * create a ColorModel to accomdate the double data
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          * create a TiledImage using the SampleModel just created
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          * create a BufferedImage from the WritableRaster and other stuff
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// **** this block is supposed ot test whether I can write the image out to a file, but I can't even reach that because of the exception*******
          File outFile = null;
          try
               outFile = new File("result.jpg");
          ImageIO.write(bufImg ,"jpg", outFile);
          } catch (IOException e)
               System.out.println("error in writing out file");
               e.printStackTrace();
               System.exit(0);
          return bufImg;
     } // end fof double2BufImage
I'm desperate for the code to perform digital watermarking.... which is only a part of my course project.... would you (anyone is welcome) provide me some light on this area...?
Thanks again.
Best,
Victor

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