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                                         931
SECTION 10.7                                                               Tagged PDF



The allocation rectangle is derived from the content rectangle in a way that also
depends on the structure type:

• For a BLSE, the allocation rectangle is equal to the content rectangle with its
  before and after edges adjusted by the element’s SpaceBefore and SpaceAfter
  attributes, if any, but with no changes to the start and end edges.
• For an ILSE, the allocation rectangle is the same as the content rectangle.
Note: Future versions of Tagged PDF are likely to include additional attributes that
can adjust all four edges of the allocation rectangle for both BLSEs and ILSEs.

Illustration Attributes

Certain additional restrictions arise in connection with particular uses of illustra-
tion elements (structure types Figure, Formula, or Form):

• When an illustration element has a Placement attribute of Block, it must have a
  Height attribute with an explicitly specified numerical value (not Auto). This
  value is the sole source of information about the illustration’s extent in the
  block-progression direction.
• When an illustration element has a Placement attribute of Inline, it must have a
  Width attribute with an explicitly specified numerical value (not Auto). This
  value is the sole source of information about the illustration’s extent in the
  inline-progression direction.
• When an illustration element has a Placement attribute of Inline, Start, or End,
  the value of its BaselineShift attribute is used to determine the position of its af-
  ter edge relative to the text baseline; BaselineShift is ignored for all other values
  of Placement. (An illustration element with a Placement value of Start can be
  used to create a dropped capital; one with a Placement value of Inline can be
  used to create a raised capital.)

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