I am new to matlab and I would really appreciate any help!
I want to implement a rectangular sliding window around a pixel and perform some operations on it. Can someone help me do the rectangular sliding window part?
Thanks in advance!
MATLAB: How to get a rectangular sliding window around a pixel
Image Processing Toolboxpixelrectangular sliding window
Related Solutions
nlfilter() slides the window across the image and applies some custom function, that you supply, to the pixels in the window. nlfilter can apply some custom function to the pixels in the window, something that conv2() cannot do.
conv2() slides the window across the image and multiplies the pixels in the window by the pixels in the filter kernel window and sums them. The output pixel is the sum. conv2() does not apply some custom function like nlfilter can.
B = A( (i - 1 : i + 1) , (i-1 : i + 1) )Consider a 3 x 3 matrix A:
A = [11 22 33 ; 44 55 66 ; 77 88 99 ];The following command will get the sub-matrix made up of the first two rows and columns of A and store that sub-matrix in B.
B = A( 1:2 , 1:2 )B = 11 22 44 55The following code is an example implementation tracking the number of times the number of windows evaluated before the success condition is met.
img = double( imread( 'trees.tif') );[ nRows , nCols ] = size( img );result = zeros( nRows , nCols );halfWinSize = 2; threshold = 50;for rI = 1:nRows for cI = 1:nCols % These indices specify the start and stop indices of the
% window. The window will go from row rILo to rIHi amd column
% cILo to cIHi
rILo = rI - halfWinSize; % lower row index of window
rIHi = rI + halfWinSize; % upper row index of window
cILo = cI - halfWinSize; % lower column index of window
cIHi = cI + halfWinSize; % upper column index of window
flagConditionMet = false ; count = 1; % while success criteria unmet
while( ~ flagConditionMet ) % It is important to make sure that your window indices are valid
% indices before pulling out the window.
if( rILo >= 1 && rIHi <= nRows && cILo >= 1 && cIHi <= nCols ) % Pull out the window around (rI , cI)
imgWindow = img( (rILo : rIHi) , (cILo : cIHi) ); %perform an operation
minVal = min( imgWindow(:) ); %check if successful
flagConditionMet = minVal < threshold; %increase window bounds if unsuccessful
if( ~ flagConditionMet ) rILo = rILo - 1; rIHi = rIHi + 1; cILo = cILo - 1; cIHi = cIHi + 1; count = count + 1; else %store some result if successful
result( rI , cI ) = count; end else % out of bounds break out of while loop
break; end end end endfigure;imshow(result./max( result(:) ))
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