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Computer Graphics

A rectangle object with coordinate values (2, 0) (5, 0), (5, 1) and (2, 1). Calculate the
values of the rectangle after it is scaled 0.5 points in X-direction and 1.5 in Y-
direction. Plot the rectangle before and after applying the scaling in 2-D space or
graph.

6.1.3 Reflection Transformation
Reflection transformation of a 2-D object creates a mirror image of the object either across the X or Y axis
of a 2-D space. The reflection transformation of an object is similar to scaling the object with a negative
scaling factor. The reflection transformation matrix to create:
−1  0
   
1. Reflection about the Y axis:  0 1 
1 0 
   
2. Reflection about the X axis:  0 −1 

−1 0 
   
3. Reflection about the origin:  0 −1 

0  1
   
4. Reflection within the same quadrant:  1 0 

The scaling factor while performing reflection transformation is 1, but the magnitude,
i.e., -1 and +1 changes with respect to the type of reflection either about X axis or Y
axis.

When the reflection transformation matrix is multiplied with the point coordinates of a 2-D object the
respective reflections are obtained, which are as shown in table 6.1.

Table 6.1: Types of Reflections

Reflection Original Object Reflected Object

About the Y
axis

Contd...

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