fast wavelet Transformation by using lowpass and highpass
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hello everyone,
I have to write a function to apply 2D FWT on an image. To do this I should:
- apply lowpass in x-direction and seperatly highpass filter also in x-direction
- on the 2 resulting images apply the lowpss and seperatly the highpass in y-direction
- I will have at the end 4 filtered images
I'm struggeling with applying the filters in one direction. Please help
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Pratyush Roy
2021-2-17
Hi Jana,
The highpass and lowpass functions can be used to perform one dimensional filtering. Let us consider the following snippet:
y = highpass(x,wpass);
Here if x is a matrix, then the function filters each column inependently. To apply filtering across a row, we can take the transpose of the input signal, compute the filtered output and take the transpose of the output again. The following snippet demonstrates the operation.
y_tr = highpass(x',wpass)
y = y_tr';
Similarly, we can perform the operation for lowpass filters.
Hope this helps!
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