a = dir('*.tif');
whos a
  Name      Size            Bytes  Class     Attributes

  a         6x1              2590  struct              

a(1).name

ans =

background.tif

M = cell(6,3);


for i=1:6,
M{i,1} = a(i).name;
M{i,2} = imread(a(i).name);
end;
for i=2:6,
M{i,3} = uint8(abs(double(M{i,2}-double(M{1,2}))));
end;
??? Error using ==> minus
Integers can only be combined with integers of the same class, or scalar doubles.

for i=2:6,
M{i,3} = uint8(abs(double(M{i,2})-double(M{1,2})));
end;
figure;
for i=1:6, subplot(2,3,i); imshow(M{i,2}); end;
figure;
for i=2:6, subplot(2,3,i); imshow(M{i,3}); end;
I = M{2,3};
Ig = rgb2gray(I);
figure; subplot(2,2,1); imhist(I(:,:,1);
??? figure; subplot(2,2,1); imhist(I(:,:,1);
                                           |
Error: Unbalanced or unexpected parenthesis or bracket.

figure; subplot(2,2,1); imhist(I(:,:,1));
subplot(2,2,2); imhist(I(:,:,2));
subplot(2,2,3); imhist(I(:,:,3));
subplot(2,2,4); imhist(Ig);
t = imthresh(Ig)
??? Undefined function or method 'imthresh' for input arguments of type 'uint8'.



help graythresh
 GRAYTHRESH Global image threshold using Otsu's method.
    LEVEL = GRAYTHRESH(I) computes a global threshold (LEVEL) that can be
    used to convert an intensity image to a binary image with IM2BW. LEVEL
    is a normalized intensity value that lies in the range [0, 1].
    GRAYTHRESH uses Otsu's method, which chooses the threshold to minimize
    the intraclass variance of the thresholded black and white pixels.
 
    [LEVEL EM] = GRAYTHRESH(I) returns effectiveness metric, EM, as the
    second output argument. It indicates the effectiveness of thresholding
    of the input image and it is in the range [0, 1]. The lower bound is
    attainable only by images having a single gray level, and the upper
    bound is attainable only by two-valued images.
 
    Class Support
    -------------
    The input image I can be uint8, uint16, int16, single, or double, and it
    must be nonsparse.  LEVEL and EM are double scalars. 
 
    Example
    -------
        I = imread('coins.png');
        level = graythresh(I);
        BW = im2bw(I,level);
        figure, imshow(BW)
 
    See also <a href="matlab:help im2bw">im2bw</a>.


    Reference page in Help browser
       <a href="matlab:doc graythresh">doc graythresh</a>

t = graythresh(Ig)

t =

    0.2196

t*255

ans =

    56



Ig_b = Ig >= 56;
figure, imshow(Ig_b);
Ig_b = Ig >= 45;
figure, imshow(Ig_b);
Ig_b = Ig >= 35;
figure, imshow(Ig_b);
tr2 = graythresh(I(:,:,1))

tr2 =

    0.2275

tr2 = graythresh(I(:,:,1))*255

tr2 =

    58

tg2 = graythresh(I(:,:,2))*255

tg2 =

    53

tb2 = graythresh(I(:,:,3))*255

tb2 =

    62

figure, imshow(I(:,:,1) >= tr2);
figure, imshow(I(:,:,2) >= tg2);
figure, imshow(I(:,:,3) >= tb2);
figure, imshow(I(:,:,3) >= tb2/2);
figure, imshow(I(:,:,1) >= tr2/2);
figure, imshow(I(:,:,2) >= tg2/2);
figure, imshow((I(:,:,1) >= tr2/2) | (I(:,:,2)>=tg2/2) | (I(:,:,3)>=tb2) );
Ib = (I(:,:,1) >= tr2/2) | (I(:,:,2)>=tg2/2) | (I(:,:,3)>=tb2); 
[i1,j1] = find(Ib > 0);
rc = sum(i1) / length(i1)

rc =

  256.4691

cc = sum(j1) / length(j1)

cc =

  360.0890

help bwmorph
 BWMORPH Morphological operations on binary image.
    BW2 = BWMORPH(BW1,OPERATION) applies a specific
    morphological operation to the binary image BW1.  
 
    BW2 = BWMORPH(BW1,OPERATION,N) applies the operation N
    times.  N can be Inf, in which case the operation is repeated
    until the image no longer changes.
 
    OPERATION is a string that can have one of these values:
       'bothat'   Subtract the input image from its closing
       'bridge'   Bridge previously unconnected pixels
       'clean'    Remove isolated pixels (1's surrounded by 0's)
       'close'    Perform binary closure (dilation followed by
                    erosion)  
       'diag'     Diagonal fill to eliminate 8-connectivity of
                    background
       'dilate'   Perform dilation using the structuring element
                    ones(3) 
       'erode'    Perform erosion using the structuring element
                    ones(3) 
       'fill'     Fill isolated interior pixels (0's surrounded by
                    1's)
       'hbreak'   Remove H-connected pixels
       'majority' Set a pixel to 1 if five or more pixels in its
                    3-by-3 neighborhood are 1's
       'open'     Perform binary opening (erosion followed by
                    dilation) 
       'remove'   Set a pixel to 0 if its 4-connected neighbors
                    are all 1's, thus leaving only boundary
                    pixels
       'shrink'   With N = Inf, shrink objects to points; shrink
                    objects with holes to connected rings
       'skel'     With N = Inf, remove pixels on the boundaries
                    of objects without allowing objects to break
                    apart
       'spur'     Remove end points of lines without removing
                    small objects completely.
       'thicken'  With N = Inf, thicken objects by adding pixels
                    to the exterior of objects without connected
                    previously unconnected objects
       'thin'     With N = Inf, remove pixels so that an object
                    without holes shrinks to a minimally
                    connected stroke, and an object with holes
                    shrinks to a ring halfway between the hold
                    and outer boundary
       'tophat'   Subtract the opening from the input image
 
    Class Support
    -------------
    The input image BW1 can be numeric or logical.
    It must be 2-D, real and nonsparse.  The output image 
    BW2 is logical.
 
    Examples
    --------
        BW1 = imread('circles.png');
        figure, imshow(BW1)
        BW2 = bwmorph(BW1,'remove');
        BW3 = bwmorph(BW1,'skel',Inf);
        figure, imshow(BW2)
        figure, imshow(BW3)
 
    See also <a href="matlab:help erode">erode</a>, <a href="matlab:help dilate">dilate</a>, <a href="matlab:help bweuler">bweuler</a>, <a href="matlab:help bwperim">bwperim</a>.


    Reference page in Help browser
       <a href="matlab:doc bwmorph">doc bwmorph</a>

diary off;