Image Pyramid

impyramid.jl

# generates a lower level of the Gaussian pyramid decomposition of an image.
function impyramid(A; sizes="downsampled")
  a = 0.375
  kernel = [1/4 - a/2, 1/4, a, 1/4, 1/4 - a/2]
  B = imfilter(imfilter(A,kernel), kernel') # slowest part of impyramid, by far

  if (sizes == "downsampled")
    return (B[1:2:end, 1:2:end])
  elseif (sizes == "both")
    return (B, B[1:2:end,1:2:end])
  end
end