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vision.Pyramid System object

Perform Gaussian pyramid decomposition

Description

The Pyramid object computes Gaussian pyramid reduction or expansion. The image reduction step involves lowpass filtering and downsampling the image pixels. The image expansion step involves upsampling the image pixels and lowpass filtering.

Note

Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Construction

gaussPyramid = vision.Pyramid returns a System object, gaussPyramid, that computes a Gaussian pyramid reduction or expansion of an image.

gaussPyramid = vision.Pyramid(Name,Value) configures the System object properties, specified as one or more name-value pair arguments. Unspecified properties have default values.

To compute a Gaussian pyramid:

  1. Define and set up your pyramid object using the constructor.

  2. Call the step method with the input image, I and the pyramid object, gaussPyramid. See the syntax below for using the step method.

J = step(gaussPyramid,I) computes J, the Gaussian pyramid decomposition of input I.

Properties

Operation

Reduce or expand the input image

Specify whether to reduce or expand the input image as Reduce or Expand. If this property is set to Reduce, the object applies a lowpass filter and then downsamples the input image. If this property is set to Expand, the object upsamples and then applies a lowpass filter to the input image.

Default: Reduce

PyramidLevel

Level of decomposition

Specify the number of times the object upsamples or downsamples each dimension of the image by a factor of 2.

Default: 1

SeparableFilter

How to specify the coefficients of low pass filter

Indicate how to specify the coefficients of the lowpass filter as Default or Custom.

Default: Default

CoefficientA

Coefficient 'a' of default separable filter

Specify the coefficients in the default separable filter 1/4-a/2 1/4 a 1/4 1/4-a/2 as a scalar value. This property applies when you set the SeparableFilter property to Default.

Default: 0.375

CustomSeparableFilter

Separable filter coefficients

Specify separable filter coefficients as a vector. This property applies when you set the SeparableFilter property to Custom.

Default: [0.0625 0.25 0.375 0.25 0.0625]

 Fixed-Point Properties

Methods

stepCompute Gaussian pyramid decomposition of input
Common to All System Objects
clone

Create System object with same property values

getNumInputs

Expected number of inputs to a System object

getNumOutputs

Expected number of outputs of a System object

isLocked

Check locked states of a System object (logical)

release

Allow System object property value changes

Examples

expand all

Read image into the workspace.

I = imread('cameraman.tif');

Perform a series of reductions. The first call reduces the original image. The other calls to impyramid use the previously reduced image.

I1 = impyramid(I, 'reduce');
I2 = impyramid(I1, 'reduce');
I3 = impyramid(I2, 'reduce');

View the original image and the reduced versions.

figure, imshow(I)

figure, imshow(I1)

figure, imshow(I2)

figure, imshow(I3)

Extended Capabilities

Introduced in R2012a