Region Adjacency Graph (RAG)
Computes region adjacency graph of a labeled 2D or 3D image.
Two regions are considered as neighbor if they are separated by a small number of pixel in the horizontal or vertical direction, as well as depth direction for 3D images.
The result is a N*2 array, containing 2 indices for each couple of neighbor regions.
usage:
ADJ = imRAG(IMG);
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]
Alternative syntax:
[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 node array is [N*3].
The algorithm proceed in scanning each line (horizontal, vertical, and in z-direction for 3D images), and by detection transitions in the labels. A background gap of width 1 pixel/voxel is assumed to exist between regions. It is possible to specify different gaps:
ADJ = imRAG(IMG, GAP);
* gap = 0 if regions are contiguous (no background),
* gap = 1, when considering the result of a watershed, for example
* gap > 1 if regions are separated by thick background (some neignborhoods can be missed)
Zitieren als
David Legland (2024). Region Adjacency Graph (RAG) (https://www.mathworks.com/matlabcentral/fileexchange/16938-region-adjacency-graph-rag), MATLAB Central File Exchange. Abgerufen .
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- MATLAB > Mathematics > Graph and Network Algorithms >
- Image Processing and Computer Vision > Image Processing Toolbox > Image Filtering and Enhancement > ROI-Based Processing >
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Inspiriert: Microscopy Image Browser (MIB), Microscopy Image Browser 2 (MIB2)
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Version | Veröffentlicht | Versionshinweise | |
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1.4.0.0 | avoid duplicate adjacencies for 3D images, update help |
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1.3.0.0 | correct processing of gap>1, and simplification of the code |
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1.2.0.0 | changes the algorithms to remove the 'diff' function, reducing the amount of memory required, and add psb to use different gaps between regions. |
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1.1.0.0 | removed dependencies to image processing toolbox, updated doc |
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1.0.0.0 |