imRAG.m File Reference

IMRAG Region adjacency graph of a labeled image. More...

Functions
function varargout =	imRAG (img, varargin)
	IMRAG Region adjacency graph of a labeled image. More...

Detailed Description

IMRAG Region adjacency graph of a labeled image.

Function Documentation

function varargout = imRAG	(		img,
			varargin
	)

IMRAG Region adjacency graph of a labeled image.

Usage

ADJ = imRAG(IMG); computes region adjacencies graph of labeled 2D or 3D image IMG. The result is a N*2 array, containing 2 indices for each couple of neighbor regions. Two regions are considered as neighbor if they are separated by a black (i. e. with color 0) pixel in the horizontal or vertical direction. ADJ has the format [LBL1 LBL2], LBL1 and LBL2 being vertical arrays the same size.

LBL1 is given in ascending order, LBL2 is given in ascending order for

each LBL1. Ex

[1 2] [1 3] [1 4] [2 3] [2 5] [3 4]

[NODES, ADJ] = imRAG(IMG); Return two arrays: the first one is a [N*2] array containing centroids of the N labeled region, and ADJ is the adjacency previously described. For 3D images, the nodes array is [N*3].

Example (requires image processing toolbox) read and display an image with several objects img = imread(coins.png); figure(1); clf; imshow(img); hold on; compute the Skeleton by influence zones using watershed bin = imfill(img>100, holes); dist = bwdist(bin); wat = watershed(dist, 4); compute overlay image for display tmp = uint8(double(img).*(wat>0)); ovr = uint8(cat(3, max(img, uint8(255*(wat==0))), tmp, tmp)); imshow(ovr); show the resulting graph [n e] = imRAG(wat); for i = 1:size(e, 1) plot(n(e(i,:), 1), n(e(i,:), 2), linewidth, 4, color, g); end plot(n(:,1), n(:,2), bo, markerfacecolor, b);

Create a basic 3D image with labels, and compute RAG germs = [50 50 50;... 20 20 20;80 20 20;20 80 20;80 80 20; ... 20 20 80;80 20 80;20 80 80;80 80 80]; img = zeros([100 100 100]); for i = 1:size(germs, 1) img(germs(i,1), germs(i,2), germs(i,3)) = 1; end wat = watershed(bwdist(img), 6); [n e] = imRAG(wat); figure; drawGraph(n, e); view(3);

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Author: David Legland e-mail: david.nosp@m..leg.nosp@m.land@.nosp@m.grig.nosp@m.non.i.nosp@m.nra..nosp@m.fr Created: 2004-02-20, Copyright 2007 INRA - BIA PV Nantes - MIAJ Jouy-en-Josas.

Referenced by ibwatershedGui>superpixelsBtn_Callback(), and mibClassifier>calcFeaturesBtn_Callback().

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