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Types of Transformations in Computer Graphics

Computer Graphics | Types of Transformations: In this tutorial, we will be explaining Translation, Rotation, Scaling, Reflection and Shearing, etc.
Submitted by Monika Sharma, on April 30, 2020

What is Transformation?

Transformation refers to the mathematical operations or rules that are applied on a graphical image consisting of the number of lines, circles, and ellipses to change its size, shape, or orientation. It can also reposition the image on the screen.

Transformations play a very crucial role in computer graphics.

Types of Transformations

There are various types of transformations in computer graphics through which an image can be processed, edited ad altered. Some basic and most commonly used types of these transformations are:

1. Translation
2. Rotation
3. Scaling
4. Reflection
5. Shearing

Translation

Translation refers to a technique in which a point is shift from one place to another, whose distance is known.

Consider a point A(x₁, y₁) be shifted to another point B (x₂, y₂). Now we only know the shifting distance t_x along x-axis and t_y along y-axis.

Now, the new coordinates (x₂, y₂) can be calculated as:

x₂ = x₁ + t_x

y₂ = y₁ + t_y

For example:

Suppose we want to shift a point with coordinates at A(30,100) and distance along x-axis is 10 units and 20 units along y-axis.

Using translation:

Here t_x = 10 ;

and t_y = 20

New coordinates A^’ (x₂, y₂):

x₂ = 30 + 10 = 130

y₂ = 100 + 20 = 120

The point will be shifted to A^’ (130, 120 ).

Rotation

Rotation refers to mathematical operation in which the graphical object is rotated about an angle (θ) to the axis.

Rotation is of two types: anti-clockwise and clockwise rotation.

Suppose we want to rotate a point with coordinates A (x₁, y₁) clockwise through an angle θ about the origin

Then the new coordinates A^’ (x₂, y₂):

x₂ = x₁ cosθ + y₁ sinθ

y₂ = x₁ sinθ - y₁ cosθ

Scaling

Scaling refers to a mathematical rule applied to change the size of the image.

If the value of scaling factors is negative, the size is decreased and when the value is positive, the size of the image is increased.

Suppose the point with coordinates A (x_1, y₁) is to be scaled by a factor s_x along the x-axis and s_y along the y-axis.

Hence the new coordinates after scaling will be:

x₂ = x₁ x s_x

y₂ = y₁ x s_y

Translation, rotation and scaling are termed as basic translations.

Other Transformations

The other two transformation techniques are as follows,

Reflection

Reflection refers to the mirror image of the original graphical object. It is an 180^o rotation operation.

Reflection can be done about following ways:

• x-axis
• y-axis
• the origin and
• A plane perpendicular to the origin

Shearing

Shearing is a transformation in which the shape of the object is slanted about the axis.

In y-shearing:

The new-coordinates will be:

x' = x

y' = y + s_y x

In x-shearing:

The new-coordinates will be:

x' = x + s_x y

y' = y