The polaroid and the wall frame both draw the photo into a window that is not
the size of the photo — the instant print shrinks it to 0.898x, the wall frame
cover-scales it by max(winW/pw, winH/ph), which is 1.47x up for a 2400x1800
source. A plain drawImageRect is nearest on CanvasKit, so that resize dropped
the edge back onto the output pixel grid: a 5 deg straighten inside a frame
exported 59.8% of its rows with the crossing pinned to the same pixel as the
row above (61.1% in the wall frame), while the same photo without a frame came
out at 55.8%.
Both draws now go through drawImageRectOptions with FilterMode.Linear, the same
call shape the straighten draw already uses. Measured on a 2400x1800 hard-edge
fixture at 5 deg, exported at the photo's own size: polaroid 59.8% -> 37.5%
flat rows, fracStd 0.336 -> 0.184; wall frame 61.1% -> 25.7%, fracStd 0.467 ->
0.210 — and the residual matches the 0.202 of the unframed export, so the
window costs nothing beyond the resample underneath it. A 45 deg edge printed
through the instant frame at 0 deg is unchanged at 0.0% flat rows.
3dtours
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