CHAPTER 4
352
Graphics
4.8.6 Inline Images
As an alternative to the image XObjects described in Section 4.8.4, “Image Dic-
inline image.
This
type of image is defined directly within the content stream in which it will be
painted rather than as a separate object. Because the inline format gives the appli-
cation less flexibility in managing the image data, it should be used only for small
images (4 KB or less).
An inline image object is delimited in the content stream by the operators
BI
(begin image),
ID
(image data), and
EI
(end image). These operators are summa-
rized in Table 4.42.
BI
and
ID
bracket a series of key-value pairs specifying the
characteristics of the image, such as its dimensions and color space; the image
data follows between the
ID
and
EI
operators. The format is thus analogous to that
of a stream object such as an image XObject:
BI
… Key-value pairs …
ID
… Image data …
EI
TABLE 4.42 Inline image operators
OPERANDS
OPERATOR
DESCRIPTION
—
—
—
BI
ID
EI
Begin an inline image object.
Begin the image data for an inline image object.
End an inline image object.
Inline image objects may not be nested; that is, two
BI
operators may not appear
without an intervening
EI
to close the first object. Similarly, an
ID
operator may
appear only between a
BI
and its balancing
EI
. Unless the image uses
ASCIIHexDecode
or
ASCII85Decode
as one of its filters, the
ID
operator should be
followed by a single white-space character, and the next character is interpreted
as the first byte of image data.
The key-value pairs appearing between the
BI
and
ID
operators are analogous to
those in the dictionary portion of an image XObject (though the syntax is differ-
ent). Table 4.43 shows the entries that are valid for an inline image, all of which