Image Processing Basics - Digital Signal Processing: Fundamentals and Applications - page 743

FIGURE 14.43

(a) Wavelet coefficients; (b) original image; (c) 16:1 compression.

for i ¼ 1:m
W1(i,:) ¼ dwt(h0,double(Y(i,:)),1) ;

'

end
for i

1:n
W1(:,i)

¼

¼ dwt(h0,W1(:,i),1); % Wavelet coefficients at level 1

end
% Quantization using 8 bits
wmax double(max(max(abs(W1)))); % Scale factor

W1 ¼ round(double(W1)*2^7/wmax); % Get 8-bit data
W1 ¼ double(W1)*wmax/2^7;% Recover the wavelet
figure (1); imshow(uint8(W1));xlabel( ' Wavelet coefcients ' );
% 8-bit quantization
[m, n] ¼ size(W1);
WW ¼ zeros(m,n);
WW(1:m/2,1:n/2) ¼ W1(1:m/2,1:n/2);
W1 ¼ WW;
% Decoding from level 1 using W1
[m, n] ¼ size(W1);
for i ¼ 1:n
Yd1(:,i) ¼ idwt(h0,double(W1(:,i)),1);
end

¼