MATLAB: How to select 100 highest coefficient from Curvelet subband image

Question

Input image size is 256×256 How to calculate number of levels required for this image size. How to select 100 highest coefficient from Curvelet subband image.

Answer 1

There are a couple ways you can do this depending on how you want to deal with repeated values. Here's a solution that finds indices for the 5 largest values (which could include repeated values):

[sortedValues,sortIndex] = sort(A(:),'descend'); 
maxIndex = sortIndex(1:5);

Here's a solution that finds the 5 largest unique values, then finds all elements equal to those values:

sortedValues = unique(A(:));          
maxValues = sortedValues(end-4:end); 
maxIndex = ismember(A,maxValues);