For example if the transform coefficients are 64- bit floating point numbers while a compression of the order of 8 bits per pixel is required then quantization is necessary.
IMAGE COMPRESS WAVELET MATLAB CODE
In case of lossy compression, quantization is done to reduce precision of the values of wavelet transform coefficients so that fewer bits are needed to code the image. medical imaging systems, as quantization is non-invertible. Quantizer: Quantization step is usually skipped if one is aiming for lossless compression, eg. Various algorithms will be covered in the next section. Thresholding is done in order to further reduce the number of significant coefficients. The image is transformed into a set of coefficients most of which are close to zero and can be eliminated which results in substantial reduction in amount of data that needs to be encoded. Wavelet Transform Stage: The advantage of wavelet transform stage can be seen in the image approximation example shown earlier. Wavelet Compresser broadly consists of three stages.
If \( k = (N+1)\), the decoder stops else we go back to step \(2\). The decoder can then decode for \(N\) output values. Typically, overhead can consist of number of input values \(N\) along with the binary string \(v\) and probability distributions. Of input values so some overhead is needed to tell the decoder where to stop. One issue with arithmetic coding is that the recursion formula in \(3\) will keep going on regardless of the number
Let us assume that system source is a discrete and finite consisting of N symbols and is given by \(S\) also known as alphabet. Lena Image Wavelet Approximation using only largest 2% coefficients Information Theory Background
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