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     CHAPTER 4                                                                 Graphics



       projected into an annotation’s target coordinate system (see Section 9.5.1, “3D
       Annotations”).


     Relationships among Coordinate Spaces

     Figure 4.4 shows the relationships among the coordinate spaces described above.
     Each arrow in the figure represents a transformation from one coordinate space
     to another. PDF allows modifications to many of these transformations.

     Because PDF coordinate spaces are defined relative to one another, changes made
     to one transformation can affect the appearance of objects defined in several
     coordinate spaces. For example, a change in the CTM, which defines the trans-
     formation from user space to device space, affects forms, text, images, and pat-
     terns, since they are all upstream from user space.


4.2.2 Common Transformations

     A transformation matrix specifies the relationship between two coordinate spac-
     es. By modifying a transformation matrix, objects can be scaled, rotated, translat-
     ed, or transformed in other ways.




                                   Form
                                   space


                  Glyph             Text
                  space            space
                                                     User             Device
                                                    space             space
                                   Image
                                   space


                                   Pattern
                                    space




                      FIGURE 4.4 Relationships among coordinate systems

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