On screen, a group (or object) with opacity, a blend mode, an opacity mask or
knockout whose content blends is drawn offscreen over a copy of its backdrop
and mixed back in by its opacity, mask and clip (a group blend mode then
applies to the backdrop-free result, as PDF defines it). Isolate Blending keeps
the content starting from transparency. Clip groups no longer isolate their
children (blending content is clipped per drawing), and non-isolated knockout
groups composite their elements against the art below the group. Groups
without blending inside still render as plain layers.
In PDF, such groups are written as non-isolated transparency groups (a
constant-alpha soft mask instead of the writer's isolated opacity group),
knockout groups included.
doc: Node::blends_through / children_blend.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
54427d7a92