Compress image with PCM encoder

For an equation like x(t) = A*sin(2*pi*f*t) the result is code like this:

% Analog signal
f=2;    % Maximum freq of the input signal
fs=5*f;
t=0:1/fs:1;
a=2;
x=a*sin(2*pi*f*t);

% Amplitude shifting
x_pos=x+a;

% Quantization
quant=round(x_pos);

% Decimal to binary
encoder=de2bi(quant, 'left-msb');

% Receiver
decoder=bi2de(encoder,'left-msb');

% Shifting the amplitude back
x_out=decoder-a;

My question is, for a given .PGM image, how can I compress it with a PCM encoder following these steps (analog signal- sampler-quantizer-encoder-decoder) and change its bits per pixel?

[Walter Roberson]

The numeric values read in by imread() can already be considered to be quantized. However if you wanted, you could quantize further. For example, you might do

quant = round(TheImage, -1);

which would round uint8 or uint16 values to the nearest 10.

encoder=de2bi(quant, 'left-msb');

For consistency you should be passing in N, the minimum number of digits to use.

[Marian-Catalin Pirvulescu]

Thank you, Walter!

For exemple, if my image is 8 bits per pixel and I want to change it to 5 bits per pixel and keep the .PGM format, how should I write the code?

Answer 1

[Pujitha Narra]

Hi,

This is one of the several submissions in MATLAB File Exchange. Feel free to contact the author of this submission directly for specific questions about the implementation.

https://www.mathworks.com/matlabcentral/fileexchange/34610-pcm-matlab-code?s_tid=answers_rc2-2_p5_MLT