Add automatic label length trimming

README.md

@@ -4,7 +4,7 @@ Kleine Flask-Weboberflaeche zum Erstellen von Etiketten und Drucken auf einem Br
 
 Die Weboberflaeche bildet die wichtigsten P-touch-Editor-Funktionen nach:
 
-- Bandbreite, Laenge, Rand und Ausrichtung
+- Bandbreite, automatische Laenge, Rand und Ausrichtung
 - frei positionierbare Objekte auf einem Etiketten-Canvas
 - Textfelder, Symbole, Rahmen/Formen, Linien und Tabellen
 - Bildimport mit Schwarz/Weiss-Konvertierung
@@ -108,6 +108,8 @@ Wenn `ptouch-print` auf deinem Setup andere Optionen braucht, nur `PRINT_COMMAND
 
 Hinweis: Der PT-P700 unterstuetzt laut Brother Auto Cut und Kettendruck, aber keinen Halbschnitt. Die Option `Kettendruck / Streifen` rendert mehrere Kopien als ein langes Druckbild, damit keine Vollschnitte zwischen den Labels entstehen.
 
+Die automatische Laenge entfernt leeres Band am Ende des Etiketts. Links bzw. oben bleibt das Layout unveraendert, damit die Positionen im Editor nachvollziehbar bleiben.
+
 ## USB testen
 
 Im laufenden Container:

app/app.py

@@ -223,6 +223,33 @@ def draw_cutmark(draw: ImageDraw.ImageDraw, width_px: int, height_px: int, scale
         y += dash + gap
 
 
+def crop_label_to_content(image: Image.Image, design: dict[str, Any], scale: float) -> Image.Image:
+    if not bool(design.get("autoLength", True)):
+        return image
+
+    tape_width = float(design.get("tapeWidthMm", 24))
+    orientation = design.get("orientation", "landscape")
+    margin_px = scaled_mm_to_px(float(design.get("marginMm", 2)), scale)
+    min_length_px = scaled_mm_to_px(10, scale)
+    black_mask = image.convert("L").point(lambda pixel: 255 if pixel < 128 else 0, "L")
+    bbox = black_mask.getbbox()
+
+    if orientation == "portrait":
+        fixed_width = scaled_mm_to_px(tape_width, scale)
+        if not bbox:
+            return new_label_image(fixed_width, min_length_px)
+        end = min(image.height, bbox[3] + margin_px)
+        target = min(image.height, max(min_length_px, end))
+        return image.crop((0, 0, image.width, target))
+
+    fixed_height = scaled_mm_to_px(tape_width, scale)
+    if not bbox:
+        return new_label_image(min_length_px, fixed_height)
+    end = min(image.width, bbox[2] + margin_px)
+    target = min(image.width, max(min_length_px, end))
+    return image.crop((0, 0, target, image.height))
+
+
 def render_design_image(design: dict[str, Any]) -> Image.Image:
     tape_width = float(design.get("tapeWidthMm", 24))
     if tape_width not in TAPE_WIDTHS_MM:
@@ -264,6 +291,8 @@ def render_design_image(design: dict[str, Any]) -> Image.Image:
         elif obj_type == "barcode":
             draw_barcode(image, obj, scale)
 
+    image = crop_label_to_content(image, design, scale)
+    draw = ImageDraw.Draw(image)
     if design.get("cutMode") in {"cutmark", "cutmark-chain"}:
         draw_cutmark(draw, image.width, image.height, scale)
 

app/static/editor.js

@@ -16,6 +16,7 @@ const state = {
   design: {
     tapeWidthMm: 24,
     lengthMm: 70,
+    autoLength: true,
     marginMm: 2,
     orientation: "landscape",
     cutMode: "auto",
@@ -31,6 +32,7 @@ const message = document.getElementById("message");
 const controls = {
   tapeWidth: document.getElementById("tapeWidth"),
   lengthMm: document.getElementById("lengthMm"),
+  autoLength: document.getElementById("autoLength"),
   marginMm: document.getElementById("marginMm"),
   cutMode: document.getElementById("cutMode"),
   copies: document.getElementById("copies"),
@@ -80,6 +82,21 @@ function printablePxPerMm() {
   return (PRINTABLE_TAPE_PX[tape] || (tape * 180) / 25.4) / tape;
 }
 
+function clamp(value, min, max) {
+  return Math.min(max, Math.max(min, value));
+}
+
+function contentLengthMm() {
+  if (!state.design.objects.length) return Number(controls.lengthMm.value) || state.design.lengthMm || 70;
+  const margin = Number(controls.marginMm.value) || 0;
+  const lengthEnd = state.design.objects.reduce((max, obj) => {
+    if (obj.hidden) return max;
+    const end = state.design.orientation === "portrait" ? obj.y + obj.h : obj.x + obj.w;
+    return Math.max(max, end);
+  }, margin);
+  return Math.ceil(clamp(lengthEnd + margin, 10, 500));
+}
+
 function selected() {
   return state.design.objects.find((obj) => obj.id === state.selectedId) || null;
 }
@@ -94,13 +111,20 @@ function syncDesignControls() {
   state.design.lengthMm = Number(controls.lengthMm.value);
   state.design.marginMm = Number(controls.marginMm.value);
   state.design.cutMode = controls.cutMode.value;
+  state.design.autoLength = controls.autoLength.checked;
   state.design.halfcut = "off";
   state.design.orientation = document.querySelector("input[name='orientation']:checked").value;
+  controls.lengthMm.disabled = state.design.autoLength;
+  if (state.design.autoLength) {
+    state.design.lengthMm = contentLengthMm();
+    controls.lengthMm.value = state.design.lengthMm;
+  }
 }
 
 function applyDesignControls() {
   controls.tapeWidth.value = state.design.tapeWidthMm;
   controls.lengthMm.value = state.design.lengthMm;
+  controls.autoLength.checked = state.design.autoLength !== false;
   controls.marginMm.value = state.design.marginMm;
   controls.cutMode.value = state.design.cutMode || "auto";
   document.querySelector(`input[name='orientation'][value='${state.design.orientation}']`).checked = true;
@@ -411,7 +435,7 @@ window.addEventListener("keydown", (event) => {
   }
 });
 
-["tapeWidth", "lengthMm", "marginMm", "cutMode"].forEach((id) => document.getElementById(id).addEventListener("input", draw));
+["tapeWidth", "lengthMm", "autoLength", "marginMm", "cutMode"].forEach((id) => document.getElementById(id).addEventListener("input", draw));
 document.querySelectorAll("input[name='orientation']").forEach((input) => input.addEventListener("change", draw));
 Object.values(controls).forEach((control) => {
   if (control && control.id && control.id.startsWith("prop")) control.addEventListener("input", applyProps);

app/static/mobile.js

@@ -2,6 +2,7 @@ const fields = {
   text: document.getElementById("mobileText"),
   tape: document.getElementById("mobileTape"),
   length: document.getElementById("mobileLength"),
+  autoLength: document.getElementById("mobileAutoLength"),
   margin: document.getElementById("mobileMargin"),
   font: document.getElementById("mobileFont"),
   copies: document.getElementById("mobileCopies"),
@@ -13,6 +14,13 @@ const fields = {
   message: document.getElementById("mobileMessage"),
 };
 
+function estimateTextLengthMm(text, fontSize, margin, frame) {
+  const lines = String(text || " ").split("\n");
+  const longest = lines.reduce((max, line) => Math.max(max, line.length), 0);
+  const textWidth = Math.max(8, longest * fontSize * 0.62);
+  return Math.min(300, Math.max(20, Math.ceil(textWidth + margin * 2 + (frame ? 4 : 0))));
+}
+
 function setMessage(text, type = "") {
   fields.message.textContent = text;
   fields.message.className = `message ${type}`;
@@ -20,9 +28,15 @@ function setMessage(text, type = "") {
 
 function mobileDesign() {
   const tapeWidth = Number(fields.tape.value);
-  const length = Number(fields.length.value);
   const margin = Number(fields.margin.value);
   const text = fields.text.value.trim() || " ";
+  const fontSize = Number(fields.font.value);
+  const autoLength = fields.autoLength.checked;
+  const length = autoLength
+    ? estimateTextLengthMm(text, fontSize, margin, fields.frame.checked)
+    : Number(fields.length.value);
+  fields.length.value = String(length);
+  fields.length.disabled = autoLength;
   const objects = [];
   if (fields.frame.checked) {
     objects.push({
@@ -44,7 +58,7 @@ function mobileDesign() {
     w: Math.max(2, length - margin * 2 - (fields.frame.checked ? 2 : 0)),
     h: Math.max(2, tapeWidth - margin * 2),
     text,
-    fontSizeMm: Number(fields.font.value),
+    fontSizeMm: fontSize,
     bold: fields.bold.checked,
     align: fields.align.value,
     valign: "middle",
@@ -52,6 +66,7 @@ function mobileDesign() {
   return {
     tapeWidthMm: tapeWidth,
     lengthMm: length,
+    autoLength,
     marginMm: margin,
     orientation: "landscape",
     cutMode: fields.cutMode.value,
@@ -89,3 +104,11 @@ document.getElementById("mobileDetect").addEventListener("click", async () => {
   fields.tape.value = String(payload.width);
   setMessage(`Band erkannt: ${payload.width} mm`, "success");
 });
+
+["text", "font", "margin", "frame", "autoLength"].forEach((name) => {
+  fields[name].addEventListener("input", () => {
+    if (name === "autoLength" || fields.autoLength.checked) mobileDesign();
+  });
+});
+
+mobileDesign();

app/templates/index.html

@@ -56,6 +56,10 @@
             Laenge
             <input id="lengthMm" type="number" min="10" max="500" step="1" value="70">
           </label>
+          <label class="check-row">
+            <input id="autoLength" type="checkbox" checked>
+            Laenge automatisch begrenzen
+          </label>
           <label>
             Rand
             <input id="marginMm" type="number" min="0" max="20" step="0.5" value="2">

app/templates/mobile.html

@@ -46,6 +46,10 @@
             <input id="mobileMargin" type="number" min="0" max="20" step="0.5" value="2">
           </label>
         </div>
+        <label class="check-row">
+          <input id="mobileAutoLength" type="checkbox" checked>
+          Laenge automatisch begrenzen
+        </label>
 
         <div class="grid-2">
           <label>