EPS export expanded the pattern fills whose tile images need flattening and
then flattened the result with flatten_document, which expanded them again
with a new object limit. PostScript printing did the same, on the layers
shown rather than the layers that print. EPS export now flattens the
expanded document without expanding it again (flatten_expanded), and
PostScript printing leaves the expansion to the flattener, which runs on
the layers that print, and only checks for such pattern fills to warn.
Blends, envelopes, repeats and Intertwine groups that hold a see-through
or colorized pattern tile image are expanded into the art the writers
draw for them before the tiles are expanded, so those tiles are
flattened too. Random Transform effects in that art are baked first.
Hidden shapes, shapes in hidden groups or layers and template layers are
skipped: expanding a hidden shape made its tiles show in the file, and
art that is not written no longer makes a flattened copy of the document.
Flattening counted every colorized image as transparency, in the art and
in pattern tiles. A new flattener option, keeps_colorize, stops counting
an image colorized with a solid paint whose pixels are grayscale or 1-bit,
for a format whose writer draws such images in their ink. Opacity,
blending modes, opacity masks and effects still flatten them, and pattern
tiles are still expanded for those. The option is off, so exports flatten
as before; the EPS writer that draws colorized images turns it on.
The EPS pattern tile tests now check the exported colors, and a tile
group with opacity for the warning.
PDF 1.3, PDF/X-1a, PDF/X-3, EPS and PostScript printing flatten
transparency with `flatten_document`, which only looked at art in the
layers. An image with see-through pixels, a colorize paint, opacity or
a blending mode drawn only through a pattern fill stayed in the pattern
definition, so the flattener returned early and the writer drew the tile
opaque and uncolorized (PDF 1.3 export failed on the transparency left).
`flatten_document` now first expands pattern fills whose tile image
needs flattening into their tiles, as legacy .ai save does. See-through
tile pixels count only where the caller counts see-through images (PDF
1.3); EPS level 3 already masks them out. The EPS and PostScript print
transparency warnings now see those tile images too.
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