Freeman chain code

Freeman chain code algorithm to extract boundaries of objects in a binary image. Help, doc, examples included. + Some bwmorph operators.

Use on binary images only (use imbinarize to binarize your image).

Check the use examples given in the file Freeman_chain_code_examples.m to help / inspire you.

Last update adds some image processing toolbox bwmorph "spare operators" you might recognize (dilate_image, erode_image, image_bw_remove, open_image, close_image), updated examples and images.

image_bw_remove function looks specially interesting to get quickly and all at once your binary image boundaries.

Please rate if it helped you. Thanks.

% Freeman_chain_code : function to extract the contour of a given shape using

% Freeman chain code. For binary images only.

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% Author & support : nicolas.douillet (at) free.fr, 2005-2022.

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% Reference

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% Freeman H, Computer Processing of Line-Drawing Images,

% ACM Computing Surveys, Vol. 6, No.1, 1974, pp57-97.

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% Inputs

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% - I : binary (0/1) image where 0 pixels correspond to the black

% background, and 1 pixels correspond to the object(s) / shape(s) to

% segment.

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% - option_display : either logical, true/false or numeric 1/0.

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% Outputs

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% - bound_img : binary (0/1) image of the input image boundaries. size(bound_img) = size(I).

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% - X0 : cell array of integer vectors of double, the boundaries initial pixels coordinates.

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% - Code : cell array of integer vectors of double, the boundaries Freeman coding vectors.

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% - bound_coord : cell array of integer vectors of double, the boundaries pixels coordinates.

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% Current known limitations

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% - Only extract the shapes outer boundaries;

% - Do not work on 'inverted' binary image (white background); in the case, just compute I = 1 - my_binary_inverted_image;

% - Do not work on images with shape(s) "touching" one of the image boundaries.