function out = logim(image,decades)

function out = logim(image,decades)
%LOGIM Image with logarithmic compression
%      out = logim(image,D);
%   produces an output image compressed to D decades.
%   D must be a non-negative integer (default 4).
%   If D is zero, no compression is performed, but the image
%   is scaled to a maximum value of 1.0.
%   If no output assignment is made, the output is displayed.

% Author: John S. Loomis (8 March 2000)

if nargin < 2
   decades = 4;
end

image = image / max(image(:));

if decades <= 0
   % truncate negative values
   v = image.*(image>0);
else
   t = 10^-decades;
   v = image.*(image>=t) + (image<t)*t;
   v = 1 + log10(v)/decades;
end

if nargout == 0
   imshow(v);
else
   out = v;
end

Maintained by John Loomis, last updated 8 March 2000