Image Processing Toolbox

Analyzing and Enhancing Images

Overview

The Image Processing Toolbox supports a range of standard image processing operations for analyzing and enhancing images. Its functions simplify several categories of tasks, including:

Obtaining pixel values and statistics, which are numerical summaries of data in an image

Analyzing images to extract information about their essential structure

Enhancing images to make certain features easier to see or to reduce noise

This section describes specific operations within each category, and shows how to implement each kind of operation using toolbox functions.

Words You Need to Know

An understanding of the following terms will help you to use this chapter. For more explanation of this table and others like it, see Words You Need to Know in the Preface.

Words
Definitions

Adaptive filter
A filter whose properties vary across an image depending on the local characteristics of the image pixels.

Contour
A path in an image along which the image intensity values are equal to a constant.

Edge
A curve that follows a path of rapid change in image intensity. Edges are often associated with the boundaries of objects in a scene. Edge detection is used to identify the edges in an image.

Feature
A quantitative measurement of an image or image region. Examples of image region features include centroid, bounding box, and area.

Histogram
A graph used in image analysis that shows the distribution of intensities in an image. The information in a histogram can be used to choose an appropriate enhancement operation. For example, if an image histogram shows that the range of intensity values is small, you can use an intensity adjustment function to spread the values across a wider range.

Noise
Errors in the image acquisition process that result in pixel values that do not reflect the true intensities of the real scene.

Profile
A set of intensity values taken from regularly spaced points along a line segment or multiline path in an image. For points that do not fall on the center of a pixel, the intensity values are interpolated.

Quadtree decomposition
An image analysis technique that partitions an image into homogeneous blocks.

Words	Definitions
Adaptive filter	A filter whose properties vary across an image depending on the local characteristics of the image pixels.
Contour	A path in an image along which the image intensity values are equal to a constant.
Edge	A curve that follows a path of rapid change in image intensity. Edges are often associated with the boundaries of objects in a scene. Edge detection is used to identify the edges in an image.
Feature	A quantitative measurement of an image or image region. Examples of image region features include centroid, bounding box, and area.
Histogram	A graph used in image analysis that shows the distribution of intensities in an image. The information in a histogram can be used to choose an appropriate enhancement operation. For example, if an image histogram shows that the range of intensity values is small, you can use an intensity adjustment function to spread the values across a wider range.
Noise	Errors in the image acquisition process that result in pixel values that do not reflect the true intensities of the real scene.
Profile	A set of intensity values taken from regularly spaced points along a line segment or multiline path in an image. For points that do not fall on the center of a pixel, the intensity values are interpolated.
Quadtree decomposition	An image analysis technique that partitions an image into homogeneous blocks.

The Inverse Radon Transform Pixel Values and Statistics