wavelet threshold select ddencmp

1.hello i want to denoise image using wavelets i think about use wavelet toolbox i want to use ddencmp but as i understand for denoise it use soft threshold always how to set hard threshold

2. i want to take only several sub images from wavelet decomposition to restore original image how to do it ? (after threshold i determine)

Answer 1

[Wayne King]

Hi ddencmp only returns thresholds so there is nothing "soft" or "hard" about it. When you actually denoise the images using wdencmp, then you want to pass the option for sorh as 's'.

You can try this out easily through the wavemenu GUI, by selecting Wavelet 2-D, importing your image, and then selecting De-Noise.

If you only want to reconstruct an approximation from certain details, you can use waverec2.m

Answer 2

[michael scheinfeild]

but what is the code for the wavemenu image denoise , it make difrent thresholds on each histogram of the wavelet coefficients

[Apoio]

I have the same question. I tried to follow the wavemenucode (sw2dtool) and I cant find where thresholds are determined, (one gets lost on the code...).

I also tried:

wname = 'haar';

level = 5;

OI=imread('test.png');

[C,S] = wavedec2(OI,level,wname);

THR = wthrmngr('dw2ddenoLVL','sqtwolog',C,S,'mln')

(the parameters ('dw2ddenoLVL','sqtwolog','mln') are as suggested by the code for denoising generated by wavemenu)

and the resulting threshold values are very different from the ones on the wavemenu GUI (and on automatically generated code).

Since the denoised image looks much better using the thresholds given by wavemenu GUI than the ones given by wthrmngr, I'd like to find out how they are computed...

TIA