97 lines
5.3 KiB
Bash
Executable File
97 lines
5.3 KiB
Bash
Executable File
#!/bin/bash
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#===============================================================================
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# generate-grub-background.sh — build the Felhom GRUB boot background (scripts v1.22.0, R-38).
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#
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# Turns Viktor's square brand card (website/assets/og-image_2.png, 1017x1016) into a GRUB-friendly
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# 1024x768 PNG. Runs INSIDE the felhom-iso-assistant container (needs ImageMagick); called by
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# iso-repack.sh.
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#
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# THE LAYOUT, AND WHY:
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#
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# * 1024x768 canvas — gfxterm-safe. The stock PVE grub.cfg already asks for `gfxmode=1024x768`, so
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# this is the mode the ISO's GRUB is known to get on real firmware. Anything larger risks a
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# fallback to 800x600 and a scaled/cropped background.
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#
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# * The card is scaled to 500x500 and composited TOP-CENTERED (y=16). That deliberately leaves the
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# bottom ~250px empty: it is where felhom-theme.txt positions the boot menu (top=70%) and the
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# countdown label (top=84%). Menu text therefore never lands on the cloud/wordmark/tagline. If
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# you change CARD or CARD_Y here, move `boot_menu.top` in felhom-theme.txt to match.
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#
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# * THE GRID. The card carries a subtle background grid (4px lines of #0D131A on #0D1117, every
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# 131px) and Viktor asked for it to stay visible. Two things could destroy it: the downscale
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# (handled — at 500/1017 the lines land at ~2px, still legible), and the letterbox fill. A flat
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# navy fill would leave an obvious 500px square of grid floating in a plain field.
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#
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# So the grid is drawn across the WHOLE canvas first, PHASE-LOCKED to where the card's own grid
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# will land, in the card's own line color — then the card is composited on top. Inside the card
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# region the card's real grid shows; outside, the drawn continuation lines up exactly. The seam
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# is invisible because the card's background (#0D1117) is also the canvas fill.
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#
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# The phase-lock math: source line centers are x=81.5+n*131, y=21.5+n*131 (measured, not guessed
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# — sampled from og-image_2.png). Scale s=CARD/SRC_W maps them onto the canvas, offset by the
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# card's origin. Line width scales the same way.
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#
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# Usage: generate-grub-background.sh <source.png> <out.png>
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#===============================================================================
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set -euo pipefail
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SRC="${1:?source card PNG required}"
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OUT="${2:?output PNG path required}"
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# --- canvas ---------------------------------------------------------------------------------------
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CW=1024; CH=768
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BG="#0D1117" # the card's own background — the letterbox must be seamless, not merely "navy"
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GRID="#0D131A" # the card's own grid line color (sampled)
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# --- card placement (keep in sync with felhom-theme.txt boot_menu.top) ------------------------------
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CARD=500; CARD_X=262; CARD_Y=16
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# --- measured properties of og-image_2.png ----------------------------------------------------------
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SRC_W=1017 # source width; the card is square (1017x1016)
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PITCH=131 # grid pitch in source px
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V0=81.5 # center of the first vertical grid line, source px
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H0=21.5 # center of the first horizontal grid line, source px
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LINE=4 # grid line width in source px
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command -v magick >/dev/null && IM=magick || IM=convert
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[[ -f "$SRC" ]] || { echo "generate-grub-background: source card not found: $SRC" >&2; exit 2; }
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# Refuse a source whose geometry no longer matches the measured constants above — a silently swapped
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# asset would misplace every grid line, and the result only shows up on a boot screen nobody re-checks.
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GEOM="$($IM identify -format '%wx%h' "$SRC")"
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[[ "$GEOM" == "1017x1016" ]] || {
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echo "generate-grub-background: source card is ${GEOM}, expected 1017x1016." >&2
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echo " The grid phase-lock constants (PITCH/V0/H0/LINE) were measured against that geometry." >&2
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echo " Re-measure them for the new asset before changing this check." >&2
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exit 3
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}
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S=$(awk -v c="$CARD" -v w="$SRC_W" 'BEGIN{printf "%.6f", c/w}') # card scale factor
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P=$(awk -v p="$PITCH" -v s="$S" 'BEGIN{printf "%.4f", p*s}') # canvas grid pitch
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LW=$(awk -v l="$LINE" -v s="$S" 'BEGIN{printf "%.2f", l*s}') # canvas grid line width
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# Walk n outward far enough to cover the canvas in both axes from the card-anchored origin.
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draw=""
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for n in $(seq -20 40); do
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x=$(awk -v a="$CARD_X" -v v="$V0" -v s="$S" -v p="$P" -v n="$n" 'BEGIN{printf "%.2f", a+v*s+n*p}')
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if awk -v x="$x" -v w="$CW" 'BEGIN{exit !(x>-2 && x<w+2)}'; then
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draw="$draw line $x,0 $x,$CH"
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fi
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y=$(awk -v a="$CARD_Y" -v v="$H0" -v s="$S" -v p="$P" -v n="$n" 'BEGIN{printf "%.2f", a+v*s+n*p}')
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if awk -v y="$y" -v h="$CH" 'BEGIN{exit !(y>-2 && y<h+2)}'; then
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draw="$draw line 0,$y $CW,$y"
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fi
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done
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[[ -n "$draw" ]] || { echo "generate-grub-background: grid draw list came out empty" >&2; exit 4; }
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# PNG24 (no palette, no alpha): GRUB's png module reads plain 8-bit RGB reliably; an indexed or
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# 16-bit PNG is where "the background silently doesn't render" comes from.
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$IM -size "${CW}x${CH}" xc:"$BG" \
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-stroke "$GRID" -strokewidth "$LW" -draw "$draw" -stroke none \
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\( "$SRC" -resize "${CARD}x${CARD}!" \) -geometry "+${CARD_X}+${CARD_Y}" -composite \
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-depth 8 "PNG24:$OUT"
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[[ -s "$OUT" ]] || { echo "generate-grub-background: produced no output" >&2; exit 5; }
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OGEOM="$($IM identify -format '%wx%h %[channels] %[depth]' "$OUT")"
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echo "generate-grub-background: $OUT ($OGEOM, $(stat -c%s "$OUT") bytes)"
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