Adobe Acrobat SDK
Implementation Notes
Adobe® Supplement to the ISO 32000
Implementation Notes to the PDF Reference, sixth edition 113
4.8.5 Masked Images
54. Explicit masking and color key masking are features of PostScript LanguageLevel 3. Acrobat 4.0 and
later versions do not attempt to emulate the effect of masked images when printing to LanguageLevel
1 or LanguageLevel 2 output devices; they print the base image without the mask.
The Acrobat 4.0 viewer displays masked images, but only when the amount of data in the mask is
below a certain limit. Above that, the viewer displays the base image without the mask.
4.9.1 Form Dictionaries
55. All Acrobat viewers ignore the
Name
entry in a form dictionary.
4.9.3 Reference XObjects
56. Acrobat 8.0 and earlier viewers do not implement reference XObjects. The proxy is always used for
viewing and printing.
5.2.5 Text Rendering Mode
57. In Acrobat 4.05 and earlier versions, text-showing operators such as
Tj
first perform the fills for all the
glyphs in the string being shown, followed by the strokes for all the glyphs. This produces incorrect
results if glyphs overlap.
5.3.2 Text-Showing Operators
58. In versions of Acrobat earlier than 3.0, the horizontal coordinate of the text position after the
TJ
operator paints a character glyph and moves by any specified offset must not be less than it was before
the glyph was painted.
59. In Acrobat 4.0 and earlier viewers, position adjustments specified by numbers in a
TJ
array are
performed incorrectly if the horizontal scaling parameter,
Th
, is different from its default value of 100.
5.5.1 Type 1 Fonts
60. All Acrobat viewers ignore the
Name
entry in a font dictionary.
61. Acrobat 5.0 and later viewers use the glyph widths stored in the font dictionary to override the widths
of glyphs in the font program itself, which improves the consistency of the display and printing of the
document. This addresses the situation in which the font program used by the conforming reader is
different from the one used by the application that produced the document.
The font program with the altered glyph widths may or may not be embedded. If it is embedded, its
widths should exactly match the widths in the font dictionary. If the font program is not embedded,
Acrobat overrides the widths in the font program on the conforming reader’s system with the widths
specified in the font dictionary.
It is important that the widths in the font dictionary match the actual glyph widths of the font program
that was used to produce the document. Consumers of PDF files depend on these widths in many
different contexts, including viewing, printing, fauxing (font substitution), reflow, and word search.
