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.
A colorized grayscale or 1-bit image draws its white pixels transparent and is written to
PDF with the image as a soft mask. Node::shows_transparency did not count it, so a PDF 1.3,
PDF/X-1a or PDF/X-3 export whose only transparency was a colorized image was not flattened
and kept the soft mask. A legacy .ai save also wrote such an image as opaque.
- shows_transparency counts a visible image with a colorize paint.
- The legacy .ai writer flattens or leaves out colorized images like other see-through images.