Help me understand the matlab bwlabel

can anybody explain me what is happening in the code below

[L,Ne]=bwlabel(Bw);
img_wk_bw_L=L==100;
img_wk_bw_L_total=img_wk_bw_L*0;

[atiqa zahid]

i want to split objects in an image in 4 images.i want help in my assignment.

[Adam Danz]

You might get more attention by starting a new question. But you'll definitely need to share at least a little bit of code to show what you've tried so far. It looks like you've been looking in the right places since you found this question.

[atiqa zahid]

% clc; % Clear the command window.

% close all; % Close all figures (except those of imtool.)

% Read the image from disk.

im1 = imread('img11_Inp.jpg');

% Test code if you want to try it with a gray scale image.

% Uncomment line below if you want to see how it works with a gray scale image.

% rgbImage = rgb2gray(rgbImage);

% Display image full screen.

%imshow(im1);

% Enlarge figure to full screen.

set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

drawnow;

% Get the dimensions of the image. numberOfColorBands should be = 3.

[rows columns numberOfColorBands] = size(im1)

%==========================================================================

% The first way to divide an image up into blocks is by using mat2cell().

blockSizeR = 128; % Rows in block.

blockSizeC = 128; % Columns in block.

% Figure out the size of each block in rows.

% Most will be blockSizeR but there may be a remainder amount of less than that.

wholeBlockRows = floor(rows / blockSizeR);

blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)];

% Figure out the size of each block in columns.

wholeBlockCols = floor(columns / blockSizeC);

blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)];

% Create the cell array, ca.

% Each cell (except for the remainder cells at the end of the image)

% in the array contains a blockSizeR by blockSizeC by 3 color array.

% This line is where the image is actually divided up into blocks.

if numberOfColorBands > 1

% It's a color image.

ca = mat2cell(im1, blockVectorR, blockVectorC, numberOfColorBands);

else

ca = mat2cell(im1, blockVectorR, blockVectorC);

end

% Now display all the blocks.

plotIndex = 1;

numPlotsR = size(ca, 1);

numPlotsC = size(ca, 2);

for r = 1 : numPlotsR

for c = 1 : numPlotsC

fprintf('plotindex = %d, c=%d, r=%d\n', plotIndex, c, r);

% Specify the location for display of the image.

subplot(numPlotsR, numPlotsC, plotIndex);

% Extract the numerical array out of the cell

% just for tutorial purposes.

rgbBlock = ca{r,c};

imshow(rgbBlock); % Could call imshow(ca{r,c}) if you wanted to.

[rowsB columnsB numberOfColorBandsB] = size(rgbBlock);

% Make the caption the block number.

caption = sprintf('Block #%d of %d\n%d rows by %d columns', ...

plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);

title(caption);

drawnow;

% Increment the subplot to the next location.

plotIndex = plotIndex + 1;

end

end

% Display the original image in the upper left.

% subplot(4, 6, 1);

% imshow(im1);

% title('Original Image');

% Inform user of next stage where we process a gray scale image.

%promptMessage = sprintf('Now I will do the same for a gray scale image.');

%titleBarCaption = 'Continue?';

%button = questdlg(promptMessage, titleBarCaption, 'OK', 'Cancel', 'OK');

%if strcmpi(button, 'Cancel')

% return;

%end

[atiqa zahid]

i put this code ...but this code creates some extra image divisions of original image.

Answer 1

[Image Analyst]

It labels the binary image so that each connected blob had an "ID number", called the label. L is an image of pixels with the value being the label that they have been assigned. For example if you have 2 blobs, the not-very-descriptively-named Ne will be 2 and each blob in L will have values of either 1 or 2 for the pixels in that blob.

The next line just creates an image of blob #100. All other blobs are removed.

The next line just creates an image of all zeros, essentially wiping away blob #100 that you just extracted. I don't know why anyone would do that. It's essentially the same as

img_wk_bw_L_total = false(size(L));

an all black/0/false binary image.