Add automatic label length trimming

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)