InDesign draws a radial gradient in the object's bounding box: on a
non-square frame it's an ellipse reaching the frame's sides, and a
Gradient Swatch tool drag keeps those proportions. LYH Studio episode 6
(3:16) gives the left page's background a radial gradient: magenta in
the middle, cyan out to every edge. DesignCraft drew a circle reaching
only the longer side, so a portrait page stayed purple at its sides.
- doc: `Fill::radial_ellipse(bounds)`: centre and radii (default: the
box's centre and half its width and height; with a tool vector, its
start, and its length measured with the box made square).
- render: the radial paint is that circle, stretched by the paint
transform; PDF: the shading's transform does the same.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
