Object Analysis

Detect edges, circles and lines; trace boundaries; perform quadtree decomposition

In an image, an edge is a curve that follows a path of rapid change in image intensity. Edges are often associated with the boundaries of objects in a scene. Different algorithms are suited for detecting edges of straight lines, round objects, or arbitrarily shaped regions. Conversely, you can detect homogenous blocks that lack edges.

Functions

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Display Boundaries

`bwboundaries`	Trace object boundaries in binary image
`bwtraceboundary`	Trace object in binary image
`visboundaries`	Plot region boundaries

Detect Circles

`imfindcircles`	Find circles using circular Hough transform
`circles2mask`	Create binary masks from circles (Since R2024a)
`viscircles`	Create circle

Detect Edges and Gradients

`edge`	Find edges in 2-D grayscale image
`edge3`	Find edges in 3-D grayscale volume
`imgradient`	Find gradient magnitude and direction of 2-D image
`imgradientxy`	Find directional gradients of 2-D image
`imgradient3`	Find gradient magnitude and direction of 3-D image
`imgradientxyz`	Find directional gradients of 3-D image

Detect Lines

`hough`	Hough transform
`houghlines`	Extract line segments based on Hough transform
`houghpeaks`	Identify peaks in Hough transform
`radon`	Radon transform
`iradon`	Inverse Radon transform

Detect Homogenous Blocks Using Quadtree Decomposition

`qtdecomp`	Quadtree decomposition
`qtgetblk`	Block values in quadtree decomposition
`qtsetblk`	Set block values in quadtree decomposition

Topics

Edge Detection
Edge detection is a technique for finding the boundaries of objects within an image.
Boundary Tracing in Images
Trace the boundaries of a single object or of all objects in a binary image.
Hough Transform
The Hough transform detects lines in an image, including lines tilted at arbitrary angles from vertical and horizontal. The Hough transform tends to be quick, but can exhibit artifacts.
Detect Lines Using Radon Transform
This example shows how to detect lines and identify the strongest lines in an image using the Radon transform.
Quadtree Decomposition
Quadtree decomposition is useful as a first step in adaptive image compression. The decomposition involves subdividing an image into homogenous blocks.