I want a differential pulse code modulation(DPCM) matlab code for images

how to apply DPCM on images

Answer 1

[Walter Roberson]

See http://www.mathworks.com/help/comm/ug/differential-pulse-code-modulation.html

You can reshape() the image array into a vector in order to create a "signal" that you apply DPCM to. It might not be very effective, but if someone promised that DPCM is useful for images then you should write the code to follow their algorithm.

[tina jain]

ok ...let me try this...

[tina jain]

see Walter sir, I used the code below

      close all;
      clear all;
      clc;
      predictor = [0 1]; % y(k)=x(k-1)
    partition = [-1:.1:.9];
    codebook = [-1:.1:1];
    y=imread('lena256.bmp');
     y=double(y);
    x = y(:);
     t = linspace(1, 2*pi, length(x));

    % Quantize x using DPCM.
    encodedx = dpcmenco(x,codebook,partition,predictor);
    % Try to recover x from the modulated signal.
    decodedx = dpcmdeco(encodedx,codebook,predictor);
    plot(t,x,t,decodedx,'--')
    xx =decodedx(:);
    [psnrtest]=psnr(x,xx)

    legend('Original signal','Decoded signal','Location','NorthOutside');

is it ok?

PSNR is only 15

[Walter Roberson]

Shrug. I am not expecting a good PSNR for arbitrarily chosen codebook and partitions and arbitrary reordering of the image into a signal.