affine transformation

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affine transformation

[ə′fīn ‚tranz·fər′mā·shən]
A function on a linear space to itself, which is the sum of a linear transformation and a fixed vector.

Affine Transformation


a pointwise mutually single-valued mapping of a plane (space) onto itself in which straight lines are transformed into straight lines. If a Cartesian coordinate system is given in a plane, then any affine transformation of this plane can be defined by means of a so-called nonsingu-lar linear transformation of the coordinates x and y of the points of this plane. Such a transformation is given by the formulas x’ = ax + by + p and y’ = cx + dy + q with the additional requirement that Affine Transformation. Analogously, any affine transformation of a space can be defined by means of nonsingular linear transformations of the coordinates of points in space. The set of all affine transformations of a plane (space) into itself forms a group of affine transformations. This denotes, in particular, that the successive execution of two affine transformations is equivalent to some single affine transformation.

Examples of affine transformations are the orthogonal transformation—a motion of a plane or space or motion with a reflection; the transformation of similitude; and uniform “compression.” A uniform “compression” with coefficient k of the plane π toward a straight line a located in it is a transformation in which the points of a remain stationary and every point M of the plane π which does not lie on a is displayed along a ray passing through M perpendicularly to a to a point M’ such that the ratio of the distances from M and M’ to a is equal to k. Analogously, one defines a uniform “compression” of space to a plane. Each affine transformation of the plane can be obtained by performing a certain orthogonal transformation and a successive “compression” on some two perpendicular lines. Any affine transformation of space can be accomplished by means of a certain orthogonal transformation and successive “compressions” on some three mutually perpendicular lines. In an affine transformation, parallel lines and planes are transformed into parallel lines and planes. The properties of the affine transformation are widely used in various branches of mathematics, mechanics, and theoretical physics. Thus, in geometry the affine transformation is used for the so-called affine classification of figures. In mechanics, it is used in the study of small deformations of continuous media; in such deformations, small elements of the medium in the first approximation undergo affine transformations.


Muskhelishvili, N. I. Kurs analiticheskoi geometrii, 4th ed. Moscow, 1967.
Aleksandrov, P. S. Lektsii po analiticheskoi geometrii. Moscow, 1968.
Efimov, N. V. Vysshaia geometriia, 4th ed. Moscow, 1961.

affine transformation

A linear transformation followed by a translation. Given a matrix M and a vector v,

A(x) = Mx + v

is a typical affine transformation.
References in periodicals archive ?
Although the CPP matching system is limited to similarity or affine transformations, because the image area used for matching are small local areas, it is believed that the basic schemes here can also cover CPP identification for moderate non-linear transformations such as projective or higher order transformations.
For the affine transformation case, the optimal CPP set contains 22 CPPs with RMS = 19.
and an affine transformation, for instance [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII].
It turns out that any particular collectionof affine transformations, when iterated randomly, produces a unique fractal figure.
Randomly iterating the corresponding set of four affine transformations generates an attractor that looks like the original leaf (right).
Photo: This scene, showing smoking chimneys ina landscape, was computed using 57 affine transformations.
The term affine transformation comes from the Latin word affinis, meaning connected with; it describes a function that maps straight lines to straight lines (Wade and Sommer 2006).
At least three points are required to determine the affine transformation parameters uniquely; however, in general, more control points are measured, and an adjustment process is employed to compute the best fitting parameters from the redundant data.
The similarity transformation is derived by adding two constraints to the affine transformation formulas.
For the affine transformation procedure, Equation (2) is rearranged as follows:
A] for the affine transformation, and a and b for the similarity transformation) from the redundant systems in Equations (6) and (7).
Step 1: An evolutive strategy is used for identifying selfsimilar contractive transformations of a given image (the problem at this stage is obtaining the selfsimilar structures within the image); the algorithm works with a population of affine transformations.