projective2d

2-D projective geometric transformation

Description

A projective2d object encapsulates a 2-D projective geometric transformation.

Creation

You can create a projective2d object using the following methods:

• fitgeotrans — Estimates a geometric transformation that maps pairs of control points between two images

• The projective2d function described here

Syntax

tform = projective2d

tform = projective2d(A)

Description

tform = projective2d creates a projective2d object with default property settings that correspond to the identity transformation.

tform = projective2d(A) sets the property T with a valid projective transformation defined by nonsingular matrix A.

Properties

T — Forward 2-D projective transformation

nonsingular 3-by-3 numeric matrix

Forward 2-D projective transformation, specified as a nonsingular 3-by-3 numeric matrix.

The matrix T uses the convention:

[x y 1] = [u v 1] * T

where T has the form:

[a b c;...
 d e f;...
 g h i];

The default of T is the identity transformation.

Data Types: double | single

Dimensionality — Dimensionality of the geometric transformation

2

Dimensionality of the geometric transformation for both input and output points, specified as the value 2.

Object Functions

invert	Invert geometric transformation
outputLimits	Find output spatial limits given input spatial limits
transformPointsForward	Apply forward geometric transformation
transformPointsInverse	Apply inverse geometric transformation

Examples

Apply Projective Transformation to Image

This example shows how to apply rotation and tilt to an image, using a projective2d geometric transformation object created directly from a transformation matrix.

Read a grayscale image into the workspace.

I = imread('pout.tif');

Combine rotation and tilt into a transformation matrix, tm. Use this transformation matrix to create a projective2d geometric transformation object, tform.

theta = 10;
tm = [cosd(theta) -sind(theta) 0.001; ...
    sind(theta) cosd(theta) 0.01; ...
    0 0 1];
tform = projective2d(tm);

Apply the transformation using imwarp. View the transformed image.

outputImage = imwarp(I,tform);
imshow(outputImage)

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• projective2d supports the generation of C code (requires MATLAB^® Coder™). For more information, see Code Generation for Image Processing.

• When generating code, you can only specify singular objects—arrays of objects are not supported.

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

• When generating code, you can only specify singular objects—arrays of objects are not supported.