A PDF-compatible .ai paints the editor's page (an opaque white rectangle the
size of the page) before its first optional-content layer and outside every
layer. It came in as art: an extra "Page 1" layer with a page-sized white path
behind the artwork, which hid white art and gave SVG/PNG/PDF exports an
opaque background.
For pages with the editor's private data (the way the importer already tells
a .ai from a PDF), the first art outside every layer, painted before any
layer, is dropped when it is a plain fill-only rectangle in an opaque,
non-spot white, with normal blending, equal to the crop box (0.5 pt
tolerance). Plain PDFs keep such a rectangle as art (as the reference app
does when opening a PDF), and so does anything else: grey, smaller or larger
rectangles, strokes, translucency, white inks, fills over the layers.
The white-cover test the soft-mask reader used is now a shared helper.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Luminosity soft masks become opacity masks (alpha masks as a white copy of
their art; backdrop colour gives Clip, an inverting transfer function Invert;
the PDF export's backdrop and Difference covers read back as the options; a
constant alpha mask is opacity). Transparency groups keep their /I and /K
flags (read by walking the content as the interpreter does). Tiling patterns
become pattern swatches (one per colour for uncoloured ones). Text becomes
point type, one object per line with a run per font and paint, fonts named
from the file (document.open textAs: text | outlines). Patch and triangle
mesh shadings become gradient meshes; gradients drawn through their grey
opacity mask get stop opacity back; shadings that don't extend clip the art.
A rectangular clip around all its art (a form's box) is dropped.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
