SECTION 4.8
341
Images
KEY
TYPE
VALUE
ImageMask
boolean
(Optional)
A flag indicating whether the image is to be treated as an image
mask (see Section 4.8.5, “Masked Images”). If this flag is
true
, the value of
BitsPerComponent
must be 1 and
Mask
and
ColorSpace
should not be
specified; unmasked areas are painted using the current nonstroking col-
or. Default value:
false
.
(Optional except for image masks; not allowed for image masks; PDF 1.3)
An image XObject defining an image mask to be applied to this image (see
to be applied to it as a color key mask (see “Color Key Masking” on page
ImageMask
is
true
, this entry must not be present. (See
(Optional)
An array of numbers describing how to map image samples
into the range of values appropriate for the image’s color space (see
ImageMask
is
true
, the array must be
either [ 0 1 ] or [ 1 0 ]; otherwise, its length must be twice the number of
color components required by
ColorSpace
. If the image uses the
JPXDecode
filter and
ImageMask
is false,
Decode
is ignored.
Default value: see “Decode Arrays” on page 344.
Mask
stream
or array
Decode
array
Interpolate
boolean
array
(Optional)
A flag indicating whether image interpolation is to be per-
formed (see “Image Interpolation” on page 346). Default value:
false
.
(Optional; PDF 1.3)
An array of alternate image dictionaries for this image
(see “Alternate Images” on page 347). The order of elements within the
array has no significance. This entry may not be present in an image XOb-
ject that is itself an alternate image.
(Optional; PDF 1.4)
A subsidiary image XObject defining a
soft-mask
image
(see “Soft-Mask Images” on page 553) to be used as a source of
mask shape or mask opacity values in the transparent imaging model. The
alpha source parameter in the graphics state determines whether the mask
values are interpreted as shape or opacity.
If present, this entry overrides the current soft mask in the graphics state,
as well as the image’s
Mask
entry, if any. (However, the other transparency-
related graphics state parameters—blend mode and alpha constant—
remain in effect.) If
SMask
is absent, the image has no associated soft
mask (although the current soft mask in the graphics state may still ap-
ply).
Alternates
SMask
stream