I have this code of embed and extract texte data into an image using DWT watermark technique with matlab .I need the know algorithm used for this code to embed a text,extract them and the steps thats used to embed and extract data,explanation of code

Data Embedding: coverImage = imread('lena.bmp'); message = importdata('minutiaTest.txt'); %message = 'Bifurcations:';

[LL,LH,HL,HH] = dwt2(coverImage,'haar'); if size(message) > size(coverImage,1) * size(coverImage,2) error ('message too big to embed'); end

bit_count = 0; steg_coeffs = [4, 4.75, 5.5, 6.25, 7];

for jj=1:size(message,2)+1 if jj > size(message,2) charbits = [0,0,0,0,0,0,0,0]; else charbits = dec2bin(message(jj),8)'; charbits = charbits(:)'-'0'; end for ii=1:8 bit_count = bit_count + 1;

        if charbits(ii) == 1
            if HH(bit_count) <= 0
                HH(bit_count) = steg_coeffs(randi(numel(steg_coeffs)));
            end
        else
            if HH(bit_count) >= 0
                HH(bit_count) = -1 * steg_coeffs(randi(numel(steg_coeffs)));
            end
        end
    end
end

stego_image = idwt2(LL,LH,HL,HH,'haar'); imwrite(uint8(stego_image),'newStego.bmp'); Data Extraction: new_Stego = imread('newStego.bmp'); [LL,LH,HL,HH] = dwt2(new_Stego,'haar'); message = ''; msgbits = ''; for ii = 1:size(HH,1)*size(HH,2) if HH(ii) > 0 msgbits = strcat (msgbits, '1'); elseif HH(ii) < 0 msgbits = strcat (msgbits, '0'); else return; end

    if mod(ii,8) == 0
        msgChar = bin2dec(msgbits);
        if msgChar == 0
            break;
        end
        msgChar = char (msgChar);
        message = [message msgChar]; 
        msgbits = '';
    end
end

[Image Analyst]

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