% -*- texinfo -*- % @deftypefn {Function File} {@var{BW2} = } bwmorph (@var{BW},@var{operation}) % @deftypefnx {Function File} {@var{BW2} = } bwmorph (@var{BW},@var{operation},@var{n}) % Perform a morphological operation on a binary image. % % BW2=bwmorph(BW,operation) performs a morphological operation % specified by @var{operation} on binary image @var{BW}. All possible % operations and their meaning are specified in a table below. % % BW2=bwmorph(BW,operation,n) performs a morphological operation % @var{n} times. Keep in mind that it has no sense to apply some % operations more than once, since some of them return the same result % regardless how many iterations we request. Those return a warning if % are called with n>1 and they compute the result for n=1. % % @var{n}>1 is actually used for the following operations: diag, % dilate, erode, majority, shrink, skel, spur, thicken and thin. % % @table @code % @item 'bothat' % Performs a bottom hat operation, a closing operation (which is a % dilation followed by an erosion) and finally substracts the original % image. % % @item 'bridge' % Performs a bridge operation. Sets a pixel to 1 if it has two nonzero % neighbours which are not connected, so it 'bridges' them. There are % 119 3-by-3 patterns which trigger setting a pixel to 1. % % @item 'clean' % Performs an isolated pixel remove operation. Sets a pixel to 0 if all % of its eight-connected neighbours are 0. % % @item 'close' % Performs closing operation, which is a dilation followed by erosion. % It uses a ones(3) matrix as structuring element for both operations. % % @item 'diag' % Performs a diagonal fill operation. Sets a pixel to 1 if that % eliminates eight-connectivity of the background. % % @item 'dilate' % Performs a dilation operation. It uses ones(3) as structuring element. % % @item 'erode' % Performs an erosion operation. It uses ones(3) as structuring element. % % @item 'fill' % Performs a interior fill operation. Sets a pixel to 1 if all % four-connected pixels are 1. % % @item 'hbreak' % Performs a H-break operation. Breaks (sets to 0) pixels that are % H-connected. % % @item 'majority' % Performs a majority black operation. Sets a pixel to 1 if five % or more pixels in a 3-by-3 window are 1. If not it is set to 0. % % @item 'open' % Performs an opening operation, which is an erosion followed by a % dilation. It uses ones(3) as structuring element. % % @item 'remove' % Performs a iterior pixel remove operation. Sets a pixel to 0 if % all of its four-connected neighbours are 1. % % @item 'shrink' % Performs a shrink operation. Sets pixels to 0 such that an object % without holes erodes to a single pixel (set to 1) at or near its % center of mass. An object with holes erodes to a connected ring lying % midway between each hole and its nearest outer boundary. It preserves % Euler number. % % @item 'skel' % Performs a skeletonization operation. It calculates a 'median axis % skeleton' so that points of this skeleton are at the same distance of % its nearby borders. It preserver Euler number. Please read % compatibility notes for more info. % % It uses the same algorithm as skel-pratt but this could change for % compatibility in the future. % % @item 'skel-lantuejol' % Performs a skeletonization operation as described in Gonzalez & Woods % 'Digital Image Processing' pp 538-540. The text references Lantuejoul % as authour of this algorithm. % % It has the beauty of being a clean and simple approach, but skeletons % are thicker than they need to and, in addition, not guaranteed to be % connected. % % This algorithm is iterative. It will be applied the minimum value of % @var{n} times or number of iterations specified in algorithm % description. It's most useful to run this algorithm with @code{n=Inf}. % % @item 'skel-pratt' % Performs a skeletonization operation as described by William K. Pratt % in 'Digital Image Processing'. % % @item 'spur' % Performs a remove spur operation. It sets pixel to 0 if it has only % one eight-connected pixel in its neighbourhood. % % @item 'thicken' % Performs a thickening operation. This operation 'thickens' objects % avoiding their fusion. Its implemented as a thinning of the % background. That is, thinning on negated image. Finally a diagonal % fill operation is performed to avoid 'eight-connecting' objects. % % @item 'thin' % Performs a thinning operation. When n=Inf, thinning sets pixels to 0 % such that an object without holes is converted to a stroke % equidistant from its nearest outer boundaries. If the object has % holes it creates a ring midway between each hole and its near outer % boundary. This differ from shrink in that shrink converts objects % without holes to a single pixels and thin to a stroke. It preserves % Euler number. % % @item 'tophat' % Performs a top hat operation, a opening operation (which is an % erosion followed by a dilation) and finally substracts the original % image. % @end table % % Some useful concepts to understant operators: % % Operations are defined on 3-by-3 blocks of data, where the pixel in % the center of the block. Those pixels are numerated as follows: % % @multitable @columnfractions 0.05 0.05 0.05 % @item X3 @tab X2 @tab X1 % @item X4 @tab X @tab X0 % @item X5 @tab X6 @tab X7 % @end multitable % % @strong{Neighbourhood definitions used in operation descriptions:} % @table @code % @item 'four-connected' % It refers to pixels which are connected horizontally or vertically to % X: X1, X3, X5 and X7. % @item 'eight-connected' % It refers to all pixels which are connected to X: X0, X1, X2, X3, X4, % X5, X6 and X7. % @end table % % @strong{Compatibility notes:} % @table @code % @item 'fill' % Checking MATLAB behaviour is needed because its documentation doesn't % make clear if it creates a black pixel if all eight-connected pixels % are black or if four-connected suffice (as we do currently following % Pratt's book). % @item 'skel' % Algorithm used here is described in Pratt's book. When applying it to % the 'circles' image in MATLAB documentation, results are not the % same. Perhaps MATLAB uses Blum's algoritm (for further info please % read comments in code). % @item 'skel-pratt' % This option is not available in MATLAB. % @item 'skel-lantuejoul' % This option is not available in MATLAB. % @item 'thicken' % This implementation also thickens image borders. This can easily be % avoided i necessary. MATLAB documentation doesn't state how it behaves. % @end table % % References: % W. K. Pratt, 'Digital Image Processing' % Gonzalez and Woods, 'Digital Image Processing' % % @seealso{dilate, erode, makelut, applylut} % @end deftypefn

- applylut % Uses lookup tables to perform a neighbour operation on binary images.
- bwmorph % Perform a morphological operation on a binary image.
- dilate % Perform a dilation morphological operation on a binary image.
- erode % Perform an erosion morphological operation on a binary image.

- bwmorph % Perform a morphological operation on a binary image.
- hough_circle % Perform the Hough transform for circles with radius @var{r} on the

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