Encode and Decode 16 bit grayscale image to jpeg2000

Question

i am trying to convert 10 bit grayscale raw image to jpeg 2000 using J2KImageWriter and i want it to convert back to grayscale raw image but when i am converting it it gives NULL.
Here is my code
public class Main {
public static void main(String[] args) {
if(args.length!=4)
System.out.println("\nEnter imagefile height width header\n");
System.exit(0);
String filename=args[0];
int height=Integer.parseInt(args[1]);
int width=Integer.parseInt(args[2]);
int header=Integer.parseInt(args[3]);
try
//reading the image data
FileInputStream imagefile=new FileInputStream(filename);
System.out.println("\nSize of image file:"+imagefile.available());
System.out.println("\nHeader:"+String.valueOf(header)+" bytes\n");
imagefile.skip(header);
short pixels[]=new short[height*width];
int i,j,k;
k=0;
for(i=0;i<height;i++)
for(j=0;j<width;j++)
int lsb=imagefile.read();
int msb=imagefile.read();
pixels[k]=(short)(msb<<8 | lsb);
k++;
//System.out.println(String.valueOf(pixels[i][j]));
imagefile.close();
DataBuffer buffer=new DataBufferUShort(pixels,width*height);
SampleModel sm=RasterFactory.createBandedSampleModel(DataBuffer.TYPE_USHORT,height,width,1);
Raster raster=RasterFactory.createWritableRaster(sm, buffer,new Point(0,0));
//imagedata reading complete
//conversion to jpeg 2000
String outfile=args[0].substring(0,args[0].lastIndexOf('.'))+".jp2";
File outimage=new File(outfile);
ImageOutputStream imout=ImageIO.createImageOutputStream(outimage);
J2KImageWriteParam j2kparam=new J2KImageWriteParam();
J2KImageWriterSpi spi=new J2KImageWriterSpi();
J2KImageWriter j2kwriter=new J2KImageWriter(spi);
j2kparam.setLossless(true);
j2kparam.setComponentTransformation(false);
j2kparam.setEncodingRate(0.5f);
j2kparam.setFilter(J2KImageWriteParam.FILTER_53);
j2kparam.setNumDecompositionLevels(3);
j2kparam.setWriteCodeStreamOnly(true);
j2kwriter.setOutput(imout);
j2kwriter.write(null,new IIOImage(raster,null,null),j2kparam);
imout.close();
J2KImageReaderSpi j2kspi=new J2KImageReaderSpi();
J2KImageReader j2kreader=new J2KImageReader(j2kspi);
ImageInputStream imin=ImageIO.createImageInputStream(outfile);
j2kreader.setInput(imin, true, false);
Raster decomp_raster=j2kreader.readRaster(1, null);
int outputdata[]=new int[width*height];
decomp_raster.getPixels(0,0,width,height,outputdata);
FileOutputStream fileout=new FileOutputStream("decomp");
for(i=0;i<height*width;i++)
short temp=(short)outputdata;
fileout.write(Short.valueOf(temp).byteValue());
Short a=new Short(Short.reverseBytes(temp));
fileout.write(a.byteValue());
fileout.close();
catch(Exception e)
System.out.println(e.getMessage());
Can anybody help me with this. Actually i need to study the performance of jpeg2000 compression using different setting of parameters.
Thanks in advance.......

Answer 1

Hi,
I am able to encode and decode the image using J2Kwriter and J2Kreader classes. But now some other issue has came up.
When compressed losslessly, the new jpeg2000 filesize is 415245 bytes. (My original file is of size 2000000 bytes)
But when i am doing lossy compression, it results in following file sizes.
Below 0.5 (encoding rate) - 535 bytes.
Greater than or equal to 0.5 - 541 bytes.
I tried with the following values of encoding rate - 0.1, 0.3, 0.5, 0.8, 1, 1000, 100000000, 500000000.
I m not able to understand why i am getting the same filesize even with different encoding rate.
How should i set the encoding rate parameter to achieve my target compression ratio.
Kindly guide me. I will be very thankful to you.
Preeti