Documentation

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

Description

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

example

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

Properties

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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 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

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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.

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) 