S E C T I O N H .3
1107
Implementation Notes
48. Acrobat viewers support the special meaning of
None
only when a
DeviceN
color space is used as a base color for an indexed color space. For
all other uses of
DeviceN
,
None
is treated as a regular spot color name.
49. This method of representing multitones is used by Adobe Photoshop 5.0.2
and subsequent versions when exporting EPS files. Beginning with ver-
sion 4.0, Acrobat exports Level 3 EPS files using this method, and can also
export Level 1 EPS files that use the “Level 1 separation” conventions of
Adobe Technical Note #5044,
Color Separation Conventions for PostScript
Language Programs.
These conventions are used to emit multitone images
as calls to “customcolorimage” with overprinting, which can then be
placed in page layout applications such as Adobe PageMaker
®
, Adobe
In-Design, and QuarkXPress.
50. Acrobat viewers earlier than version 4.0 do not display patterns on the
screen, although they do print them to PostScript output devices.
51. Acrobat viewers that encounter an XObject of an unknown type display
an error specifying the type of XObject but report no further errors there-
after.
52. Image XObjects in PDF 1.2 and earlier versions are all implicitly un-
masked images. A PDF consumer that does not recognize the
Mask
entry
treats the image as unmasked without raising an error.
53. All Acrobat viewers ignore the
Name
entry in an image dictionary.
54. Explicit masking and color key masking are features of PostScript Lan-
guageLevel 3. Acrobat 4.0 and later versions do not attempt to emulate the