WP test container created

tools/cut-parchment.py

@@ -0,0 +1,90 @@
+"""Convert the submenu master into the theme's 9-slice parchment.
+
+The tile is the master, whole: 1200x450, converted to WebP and otherwise
+untouched. That sounds like doing nothing, and the reason it is right is worth
+recording, because two earlier versions of this file did a great deal.
+
+A 9-slice needs only a 36px border and a small middle, so the obvious cut is
+328x328 — one tiny file for any panel at any height. But cutting it that narrow
+means manufacturing seven junctions that do not exist in the artwork, and the
+master's drop shadow is *directional*: at the same distance from the border the
+four edges differ by 20-35 luminance levels (left 192 against top 157 at k=12),
+converging only as they reach the interior. Reused edges and pasted corners
+therefore cannot agree, and the corners showed it:
+
+    top-left    | left slab     41.9      <- worst
+    bottom-left | bottom slab   27.7
+    bottom-left | left slab     24.3
+    top-right   | top slab      15.1
+    bottom-right| bottom slab    1.9
+
+Twenty times worse at one corner than another. Levelling does not rescue it:
+correcting every rim piece onto one shared cross-edge profile still left the
+worst junction at 15, and flattened the shadow's direction to get there. Worse,
+each correction fights the others — wrapping a slab so it tiles moves its ends
+away from the corners above and below it, which is the same defect again.
+
+Keeping the master whole removes the problem instead of correcting it. Every
+piece is contiguous with its neighbours because they were never cut apart, so
+there is nothing to level, nothing to wrap, and nothing to flatten.
+
+What this costs, and why it is still the right trade:
+
+  * `border-image-repeat: round` scales a slab so a whole number fits. The
+    middle is 1128x378, and a panel up to about 460px tall needs exactly one
+    repeat — no join anywhere. The demo's panels are 280-460px.
+  * Above roughly 640px the vertical count rounds to 2 and a join appears in
+    the left and right borders. That happens on a phone, where the panels stack
+    and run long. The join is untreated; the alternative was a treated join at
+    every corner of every panel, which is the defect this replaces.
+  * Horizontally, a 1200px panel needs 0.99 repeats: no join at the site width.
+    On a phone the 1128px edge art is squeezed to about 358px, so the tear
+    reads finer. That is a scale change, not a seam.
+
+WebP at quality 90 rather than lossless: the artwork is a soft shadow over a
+grain of std 2, which the encoder carries at a third of the size.
+"""
+import numpy as np
+from PIL import Image
+
+SRC = '/home/jasa/PycharmProjects/wp-migrate/site/wp-content/uploads/2019/10/papyrus_submenu_450_cnd.png'
+OUT = '/home/jasa/PycharmProjects/tlig_css/src/images/parchment.webp'
+
+# Must match `border-image-slice` in abstracts/_mixins.scss.
+SLICE = 36
+QUALITY = 90
+
+im = Image.open(SRC).convert('RGBA')
+W, H = im.size
+im.save(OUT, quality=QUALITY, method=6)
+
+import os
+print('wrote %s  %dx%d  %.1f KB' % (OUT, W, H, os.path.getsize(OUT) / 1024))
+
+# Diagnostics. Nothing here is corrected — these are the numbers that would
+# tell us the master had changed, or that a panel size had moved outside the
+# range where the middle needs a single repeat.
+t = np.asarray(Image.open(OUT).convert('RGBA')).astype(np.float32)
+
+
+def level(band):
+    """Alpha-weighted mean luminance, so the transparent rim does not count."""
+    w = band[..., 3] / 255.0
+    return float((band[..., :3].mean(axis=2) * w).sum() / (w.sum() + 1e-6))
+
+
+print('  every piece is contiguous; junction steps are the master\'s own:')
+for name, a, b in (
+    ('top-left | left slab', t[SLICE-4:SLICE, 4:SLICE-4], t[SLICE:SLICE+4, 4:SLICE-4]),
+    ('bottom-left | left slab', t[H-SLICE-4:H-SLICE, 4:SLICE-4], t[H-SLICE:H-SLICE+4, 4:SLICE-4]),
+    ('top-right | right slab', t[SLICE-4:SLICE, W-SLICE+4:W-4], t[SLICE:SLICE+4, W-SLICE+4:W-4]),
+    ('bottom-right | right slab', t[H-SLICE-4:H-SLICE, W-SLICE+4:W-4], t[H-SLICE:H-SLICE+4, W-SLICE+4:W-4]),
+):
+    print('    %-30s %5.1f' % (name, abs(level(a) - level(b))))
+
+mid_h, mid_w = H - 2 * SLICE, W - 2 * SLICE
+print('  middle slab %dx%d — repeats needed by `round`:' % (mid_w, mid_h))
+for h in (280, 380, 460, 640, 900, 1600):
+    n = max(1, round((h - 2 * SLICE) / mid_h))
+    print('    panel %4dpx tall -> %d repeat%s%s'
+          % (h, n, '' if n == 1 else 's', '' if n == 1 else '  (a join appears)'))