SECTION 7.5
555
Specifying Transparency in PDF
KEY
RESTRICTION
Width
If a
Matte
entry (see Table 7.12, below) is present, must be the
same as the
Width
value of the parent image; otherwise inde-
pendent of it. Both images are mapped to the unit square in
user space (as are all images), regardless of whether the sam-
ples coincide individually.
Same considerations as for
Width
.
Required; must be
DeviceGray
.
Required.
Ignored.
Must be
false
or absent.
Must be absent.
Must be absent.
Default value:
[ 0 1 ]
.
Optional.
Ignored.
Ignored.
Ignored.
Ignored.
Ignored.
TABLE 7.12 Additional entry in a soft-mask image dictionary
Height
ColorSpace
BitsPerComponent
Intent
ImageMask
Mask
SMask
Decode
Interpolate
Alternates
Name
StructParent
ID
OPI
KEY
TYPE
VALUE
Matte
array
(Optional; PDF 1.4)
An array of component values specifying the matte color with
which the image data in the parent image has been preblended. The array consists of
n
numbers, where
n
is the number of components in the color space specified by the
ColorSpace
entry in the parent image’s image dictionary; the numbers must be valid
color components in that color space. If this entry is absent, the image data is not
preblended.