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                                                 212
            CHAPTER 4                                                                    Graphics



PARAMETER           TYPE               VALUE

soft mask           dictionary         (PDF 1.4) A soft-mask dictionary (see “Soft-Mask Dictionaries” on
                    or name            page 552) specifying the mask shape or mask opacity values to be
                                       used in the transparent imaging model (see “Source Shape and
                                       Opacity” on page 526 and “Mask Shape and Opacity” on page 550),
                                       or the name None if no such mask is specified. This parameter is
                                       implicitly reset to its initial value at the beginning of execution of a
                                       transparency group XObject (see Section 7.5.5, “Transparency
                                       Group XObjects”). Initial value: None.

alpha constant      number             (PDF 1.4) The constant shape or constant opacity value to be used
                                       in the transparent imaging model (see “Source Shape and Opacity”
                                       on page 526 and “Constant Shape and Opacity” on page 551). There
                                       are two separate alpha constant parameters: one for stroking and
                                       one for all other painting operations. This parameter is implicitly
                                       reset to its initial value at the beginning of execution of a transpar-
                                       ency group XObject (see Section 7.5.5, “Transparency Group
                                       XObjects”). Initial value: 1.0.

alpha source        boolean            (PDF 1.4) A flag specifying whether the current soft mask and al-
                                       pha constant parameters are to be interpreted as shape values (true)
                                       or opacity values (false). This flag also governs the interpretation of
                                       the SMask entry, if any, in an image dictionary (see Section 4.8.4,
                                       “Image Dictionaries”). Initial value: false.


                        TABLE 4.3 Device-dependent graphics state parameters
PARAMETER           TYPE               VALUE

overprint           boolean            (PDF 1.2) A flag specifying (on output devices that support the
                                       overprint control feature) whether painting in one set of colorants
                                       should cause the corresponding areas of other colorants to be
                                       erased (false) or left unchanged (true); see Section 4.5.6, “Overprint
                                       Control.” In PDF 1.3, there are two separate overprint parameters:
                                       one for stroking and one for all other painting operations. Initial
                                       value: false.

overprint mode      number             (PDF 1.3) A code specifying whether a color component value of 0
                                       in a DeviceCMYK color space should erase that component (0) or
                                       leave it unchanged (1) when overprinting (see Section 4.5.6, “Over-
                                       print Control”). Initial value: 0.

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