DWT

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mary
mary 2011-2-24
回答： moahaimen talib 2017-2-15
Hi i m mary .my project topic is Digital watermarking on fingerprint.i am using matlab ,i m appliying DWT on fingerprint image .bt i have some confusions plz answer my following questions 1:what are LL,LH,HL,HH in DWT? 2:what is difference between Subimage and subband? 3:why we divide the approximation band? 4:what will be the threshold value? 5:should we convert image into matrix before applying DWT?

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回答（4 个）

shyama p
shyama p 2011-3-17
Dwt is the algorithm used to reduce dimensionality of image so it used for image compression, feature extraction process. DWT algorithm decomposes the image into 4 subband (subimage) ie,LL,LH,HL,HH. dwt output extract the detailed ouput of input image. LL is the approximate image of input image it is low frequency subband so it is used for further decomposition process.. LH subband extract the horizontal features of original image HL subband gives vertical features HH subband gives diagonal features
LH,HL,HH are high frequency subbands
[LL,LH,HL,HH] = DWT2(X,'db5') % x is input image
figure;imshow(LL); % shows LL subband
hamza khalid
hamza khalid 2015-4-24
hello i am going to do feature extractions of EEg signals regarding to left and right hand movement i apply DWT technique so what are the required features which i have to extract any answer
Ghassan Hajj Hassan
Your question about why we divide the approximation band LL, is because it contains the highest quantity of information, so you divide it to get the most of the most valuable quantity of information from the image LL1,LL2,LL3,...
moahaimen talib
moahaimen talib 2017-2-15
how to divide an image in to 4 chanels showing it as table

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