%------------------------------------------------------------%
%-------- Matlab Image Intensity Levels converter -----------%
%------------------------------------------------------------%
%
%  !!!! TIF version !!!!
%
% V0.20 2004/12/16
% Changelog:
% from V0.11 (2004/12/16)to V0.20: removed extrapolation for dynamic range < 256
% from V0.1 (2004/12/15) to V0.11: added +0.5 for correct rounding
%
%
%
% Description:
% This Matlab script can be used to convert a 16-bit tif image into a 8bit*
% tif or jpg (100% quality) by defining the intensity range equivalent to
% 0.."256" (if the dynamic range before is greater than 256 intensity levels, the 
%           levels are lowered linearly otherwise the dynamic range is kept the 
%           same but clipped within 256 intensity levels)
%  (*: the bit level may be adjusted too if desired - possible with tif images)
%
%
% Input arguments: 
%       1st: "path" - path string to the folder where the images to be converted
%                     are contained (e.g. 'c:\pivimg\')
%       2nd: "Imin" - original level equivalent to 0
%       3rd: "Imax" - original level equivalent to 255
%
% Example 1:
%  to convert the original levels ranged 100 to 500 into 0 to 255
% (linearly interpolated / shifted) with all files in folder 'd:\myimages\'
% type: LevelConv('d:\myimages\', 100, 500)
% the intensity level 100 will now correspond to 0 and 500 to 255, with all levels 
% inbetween interpolated linearly
%
% Example 2:
% if the original levels now ranged 100 to 200
% type: LevelConv('d:\myimages\', 100, 200)
% the intensity level 100 will now correspond to 0 and 200 to 100, with all 
% original levels <100 now being zero and the ones  >355 now equal to 255;
% the reason for this is not to artificially increase the actual dynamic range and
% thus introduce additional potential errors
%
%
% basic function description (based on the assumption of a 16 bit tif originating 
% from a 10 bit camera and shifted by multiplication with 2^6)
% note images aquired with a different software than epix might behave differently
% 1. the 16-bit tif is read
% 2. the 16-bit tif is shifted to 10 bit by multiplication with 2^-6
% 3. the lower level is set to zero by subtracting the lower level (e.g. 100)
% 4. the range of 0-255 is achieved by multiplication (linear shifting)


function LevelConv(path, Imin, Imax)     % function definition

% Adjustable parameters
imgReadFormat = 'tif';  % format of image to read, choose from: 'tif', 'jpg', ...
imgWriteFormat = 'tif'; % format to write the image to; carefull: set quality etc
                        % as well!
PicResBit = 16;         % picture resolution
CamResBit = 10;         % camera resolution in bit

% adjust Imax  (new in V0.20)
if ((Imax - Imin) < 255)
   Imax = Imin + 255;
end;

% get files from path
 files = dir ([path, '*.', imgReadFormat]);

% process all files in the path
for i=1:size(files,1)
   X = imread([path,files(i).name]); % read a particular image file
   ImgFName = [path, '8bit', ...
       files(i).name(1:findstr(files(i).name,imgReadFormat)-1), imgWriteFormat]  
% image file name to be written display not suppressed to allow viewing progress
   X = uint8( ( double(X)*2^(CamResBit-PicResBit) - Imin ) ...
                /(Imax-Imin)*255 + 0.5); % image manipulation as described
       % note any levels above 255 will be cropped to 255 as unlike other software
       % Matlab won't rebegin at zero due to bit shifting (makes life easier)
   imwrite(X,ImgFName,imgWriteFormat); % writing the new image
end