aspect ratio and keep awake

README.md

@@ -56,6 +56,21 @@ When idle for 5 minutes, a fish-tank screensaver protects the CRT from burn-in.
    Add `--windowed` to test in a window instead of fullscreen.
    **Press Esc or Q to quit.**
 
+## Running headless (lid closed)
+
+While it is running, the booth holds systemd keep-awake locks
+(`systemd-inhibit`, block mode: `sleep`, `idle`, and `handle-lid-switch`
+when no desktop environment already holds it). The laptop will not suspend
+or idle-sleep, and — on machines where logind manages the lid — closing
+the lid does nothing, so the laptop can run tucked away behind the CRT.
+The locks are released as soon as the program exits.
+
+If the machine still suspends when the lid closes (some desktop
+environments keep the lid lock for themselves), disable lid suspend on
+that machine: put `HandleLidSwitch=ignore` in
+`/etc/systemd/logind.conf.d/photobooth.conf` (needs root, applies even
+when the booth is not running) or use the desktop's own power settings.
+
 ## Customizing
 
 - **All settings** live in `config.toml` — camera choice, screen text,
@@ -84,9 +99,10 @@ To use a different camera:
   automatically after a successful print. (If the program is restarted
   mid-cycle, photos here are counted so no progress is lost.)
 - `contact_sheets/` — every printed sheet, kept as a backup in case of
-  printer trouble. Delete them manually now and then, or set
+  printer trouble. Sheets are full US-letter pages at 300 DPI, so they
-  `delete_contact_sheets = true` in the config to remove each one right
+  also print at the right size from any other app. Delete them manually
-  after it prints.
+  now and then, or set `delete_contact_sheets = true` in the config to
+  remove each one right after it prints.
 
 ## If printing fails
 

contact_sheet.py

@@ -17,7 +17,9 @@ that maximizes each printed photo's area on a fixed 8.5x11 letter sheet
                         a strip has few photos and a wide page fills better
                         (e.g. 1 photo per shoot, or one big photo).
 
-The date is printed only inside the footer.
+The date is printed only inside the footer. Sheets are saved with 300-DPI
+metadata so their physical print size is well-defined (a full letter page)
+for CUPS or any other program they are printed from.
 """
 
 import subprocess
@@ -229,13 +231,24 @@ def build_sheet(photo_paths, out_path, footer_cfg=None,
     for (x, y, w, h) in layout["footer_rects"]:
         sheet.paste(footer_img, (x, y))
 
-    sheet.save(out_path, quality=95)
+    # Stamp 300 DPI into the file: without it the sheet has no defined
+    # physical size and the print pipeline has to guess (and may stretch).
+    sheet.save(out_path, quality=95, dpi=(300, 300))
     return out_path
 
 
 def print_sheet(path, printer=""):
-    """Send the sheet to the printer via lp. Returns (ok, message)."""
+    """Send the sheet to the printer via lp. Returns (ok, message).
-    cmd = ["lp", "-o", "media=letter", "-o", "fit-to-page"]
+
+    fit-to-page scales uniformly, so the sheet's aspect ratio is preserved.
+    Passing the sheet's orientation explicitly keeps a landscape sheet from
+    being rotated or squeezed by driver defaults.
+    """
+    with Image.open(path) as im:
+        sheet_w, sheet_h = im.size
+    orientation = "landscape" if sheet_w > sheet_h else "portrait"
+    cmd = ["lp", "-o", "media=letter", "-o", "fit-to-page",
+           "-o", orientation]
     if printer:
         cmd += ["-d", printer]
     cmd.append(str(path))

photobooth.py

@@ -6,10 +6,17 @@ CAPTURING (countdowns, flashes, 3 photos per shoot). Every 4th shoot the
 12 photos are composed onto a contact sheet and printed. Five minutes of
 inactivity brings up the fish tank screensaver.
 
+While running, the booth re-execs itself under systemd-inhibit so the
+machine will not sleep or suspend (and, when the lock is available, ignores
+the laptop lid) - it can run headless with the lid closed.
+
 Run with --windowed for testing without taking over the display.
 Esc or Q quits.
 """
 
+import os
+import shutil
+import subprocess
 import sys
 import time
 import tomllib
@@ -26,6 +33,51 @@ ROOT = Path(__file__).resolve().parent
 
 IDLE, PREVIEW, COUNTDOWN, FLASH, SCREENSAVER = range(5)
 
+KEEP_AWAKE_ENV = "PHOTOBOOTH_INHIBITED"
+KEEP_AWAKE_WHY = "Photobooth is running (keep awake, ignore lid)"
+
+
+def _probe_inhibit_locks():
+    """Largest lock set systemd-inhibit can hold on this machine.
+
+    Returns a --what value like "sleep:idle:handle-lid-switch", or None when
+    systemd-inhibit is missing or no lock can be taken. handle-lid-switch
+    allows only one block holder, so it is skipped when a desktop
+    environment already holds it. Each probe runs `true` under the lock, so
+    locks are taken and released instantly.
+    """
+    inhibit = shutil.which("systemd-inhibit")
+    if not inhibit:
+        return None
+    for what in ("sleep:idle:handle-lid-switch", "sleep:idle", "sleep"):
+        probe = subprocess.run([inhibit, "--mode=block", f"--what={what}",
+                                "--", "true"], capture_output=True)
+        if probe.returncode == 0:
+            return what
+    return None
+
+
+def reexec_keep_awake():
+    """Re-exec this process under systemd-inhibit (once) so the machine
+    stays awake - and ignores the lid when that lock is free - while the
+    booth runs. Locks are released when the program exits. Best-effort:
+    hosts without systemd-inhibit simply run without locks."""
+    if os.environ.get(KEEP_AWAKE_ENV):
+        return
+    what = _probe_inhibit_locks()
+    if not what:
+        return
+    os.environ[KEEP_AWAKE_ENV] = "1"
+    argv = [shutil.which("systemd-inhibit"), "--mode=block",
+            f"--what={what}", f"--why={KEEP_AWAKE_WHY}", "--",
+            sys.executable, str(ROOT / "photobooth.py"), *sys.argv[1:]]
+    # flush: execvp replaces the process without draining stdout's buffer.
+    print(f"Keep-awake: re-running under systemd-inhibit ({what})", flush=True)
+    try:
+        os.execvp(argv[0], argv)
+    except OSError as e:
+        print(f"Keep-awake: re-exec failed ({e}); running without locks")
+
 
 def load_config():
     with open(ROOT / "config.toml", "rb") as f:
@@ -290,6 +342,7 @@ class Booth:
 
 
 def main():
+    reexec_keep_awake()
     windowed = "--windowed" in sys.argv
     booth = Booth(windowed=windowed)
     try:

test_contact_sheet.py

@@ -92,12 +92,13 @@ def check_layout_combos():
             assert ys == sorted(ys), f"pps={pps} spp={spp} strip {strip_i}: not top-to-bottom"
             for a, b in zip(rects, rects[1:]):
                 assert b[1] >= a[1] + a[3], "photos overlap vertically"
-            # Cell aspect must match the chosen mode.
+            # Cell aspect must be exactly 4:3 (3:4 when rotated) to match
+            # the captured photos, within integer rounding of the layout.
             cw, ch = rects[0][2], rects[0][3]
-            if layout["mode"] == "portrait_ccw":
+            want = 3 / 4 if layout["mode"] == "portrait_ccw" else 4 / 3
-                assert ch >= cw, f"portrait_ccw cell not taller than wide"
+            assert abs(cw / ch - want) < 0.02, (
-            else:
+                f"pps={pps} spp={spp} {layout['mode']}: cell {cw}x{ch} "
-                assert cw >= ch, f"landscape_none cell not wider than tall"
+                f"aspect {cw / ch:.4f} != ~{want:.4f}")
 
         # Footer sits below the column, aligned in x, same width.
         for strip_i in range(spp):
@@ -121,7 +122,11 @@ def check_layout_combos():
                            margin=120, photo_gutter=30, strip_gutter=30,
                            auto_orient=True)
             from PIL import Image as _I
-            sheet = _I.open(out).convert("RGB")
+            with _I.open(out) as opened:
+                dpi = opened.info.get("dpi", (0, 0))
+                assert abs(dpi[0] - 300) <= 1 and abs(dpi[1] - 300) <= 1, \
+                    f"sheet dpi metadata wrong: {dpi} (want ~300)"
+                sheet = opened.convert("RGB")
             assert sheet.size == (page_w, page_h)
 
             for i, r in enumerate(layout["photo_rects"]):