Image processing ;quantize coder and decoder needed urgentily

hi friends...I have used a dwt2 on an grayscale image in 5 levels and its gave me large numbers up to 7000 as maximum,I need to use smaller numbers in my work (neer 256 or 512 as maximum) but I am also restricted to have large PSNR and small Compression ratio so I used quatization to reduce the values but I still have problems with the amount of my data so I used the follwoing code for quantization:

 c1=c;               %c is the input data
 MAXc=max(c1);
 MINc=min(c1);
 MAXc=round(MAXc);
 MINc=round(MINc);
 v1=mod(MAXc,2);
 v2=mod(MINc,2); if v1==1 MAXc=MAXc+1;  end if v2==1  MINc=MINc-1;  end partition = [MINc:8:MAXc];

codebook = [(MINc/2)-4:4:(MAXc/2)];

[index,quants] = quantiz(c1,partition,codebook);

c=quants; % the output data

(where the c is the result of the 5 levels dwt2 on Lena image) I also need the dequantization step which I don't know how to write it...I hope that I explained my problem clearly I be very thankful to anybody can help me...