i've divided the image into non-overlapping blocks and i want to calculate the mean of every block...

2013 2 14
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after calculating the mean i;ve to store it in array corresponding to their block number
plz tell me how to do?
Mean=[];
for row = 1 : blockSizeR : rows
for col = 1 : blockSizeC : columns
row1 = row;
row2 = row1 + blockSizeR - 1;
row2 = min(rows, row2);
col1 = col;
col2 = col1 + blockSizeC - 1;
col2 = min(columns, col2);
oneBlock = grayImage(row1:row2, col1:col2);
m=mean(mean(oneBlock));
M=m;
Mean=[Mean;M];
disp(Mean);
end
end
the above code shows only the mean value... but i want that it also shows the block number corresponding to the mean value...
plz rectify or modify the above code in order to do so.

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Image Analyst
Image Analyst 2013-2-14

0 个投票

Not sure how you want to define block number but how about:
blockNumber = 1;
for row = 1 : blockSizeR : rows
for col = 1 : blockSizeC : columns
row1 = row;
row2 = row1 + blockSizeR - 1;
row2 = min(rows, row2);
col1 = col;
col2 = col1 + blockSizeC - 1;
col2 = min(columns, col2);
oneBlock = grayImage(row1:row2, col1:col2);
Mean(blockNumber) = mean2(oneBlock);
fprintf('The mean for block #%d = $f', ...
blockNumber, Mean(blockNumber));
blockNumber = blockNumber + 1;
end
end

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angel
angel 2013-2-14
编辑：angel 2013-2-14
thank u sir....it works as i wanted...now i m trying to sort the mean values...m applying the sort function....i want output in the form as:
mean of block 1 =12.34
mean of block 2= 6.78
mean of block 3= 34.56
mean of block 4=3.56
after applying sort function i want this to be as:
mean of block 4 =3.56
mean of block 2 = 6.78
mean of block 1 = 12.34
mean of block 3 = 34.56
angel
angel 2013-2-14
blockNumber = 1;
for row = 1 : blockSizeR : rows
for col = 1 : blockSizeC : columns
row1 = row;
row2 = row1 + blockSizeR - 1;
row2 = min(rows, row2);
col1 = col;
col2 = col1 + blockSizeC - 1;
col2 = min(columns, col2);
oneBlock = grayImage(row1:row2, col1:col2);
Mean(blockNumber) = mean2(oneBlock);
fprintf('The mean for block #%d = $f', ...
blockNumber, Mean(blockNumber));
blockNumber = blockNumber + 1;
end
end
S=sort(Mean);
fprintf('\nBlock # %d = %f',blockNumber,S);
but output is not as per i want... help me sir...
Image Analyst
Image Analyst 2013-2-14
You have to take both return arguments of sort(), not just one.
angel
angel 2013-2-15
can u code it sir for me plz.... u mean
S=sort(Mean(blockNumber);
fprintf('\nblock #%d = %f',blockNumber,S);
if not, correct it plz
Walter Roberson
Walter Roberson 2013-2-15
[S, blockNumber] = sort(Mean);
fprintf('\nBlock #%d = %f', [blockNumber(:), S(:)].' );
angel
angel 2013-2-15
编辑：Image Analyst 2013-2-15
thank u so much sir :)
ur help means a lot to me.

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更多回答（2 个）

Abbas Cheddad
Abbas Cheddad 2013-2-14

1 个投票

Hi there,
You could do the following:
%%%%%%%%%%%%%
fun = @(block_struct) mean2(block_struct.data);
I2 = blockproc(A,[8 8],fun);
Block_Mean(:,1)=reshape(I2,[1 size(I2,1)*size(I2,2)]);
Block_Mean(:,2)=1:length(Block_Mean);
%%%%%%%%%%%%%%
Where "A" denotes your image and [8 8] is the size of the block of your choice. This will result in "Block_Mean" which holds the mean intensity and the corresponding block number.

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angel
angel 2013-2-14
@ Abbas: ya sir but block_proc returns single image after processing all the blocks..i've given the code above i have modified it as the image anaylst told me... i m trying to applying the sort function but not stricking to me how to apply
Abbas Cheddad
Abbas Cheddad 2013-2-14
Block_proc returns a single image with the same size as "A" if you use the documented code as in:
fun = @(block_struct) ...
mean2(block_struct.data) * ones(size(block_struct.data));
But in the code I have given you, each pixel in "I2" corresponds to the mean of a single block.
Anyhow, since what you have in hand works for you then happy days!

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Jan
Jan 2013-2-14

0 个投票

The fast C-MEX function FEX: BlockMean performs this operation.
R = BlockMean(img, blockSizeR, blockSizeC);

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angel
angel 2013-2-14
this shows error:
Undefined function 'BlockMean' for input arguments of type 'uint8'. input image is 256 x 256
sir plz help me in sorting the mean values which i've calculated...
plz go through the above code that i've mentioned and tell me..
Walter Roberson
Walter Roberson 2013-2-15
You need to download and install that code in order to have a BlockMean routine.

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