Logo-Hoehe via image_dimensions() berechnen, Firmendaten korrekt darunter

app.py

@@ -6,6 +6,7 @@ Bietet eine Weboberflaeche zur Eingabe von Druckparametern,
 Live-Berechnung der Kosten, PDF-Rechnung und TXT-Export.
 """
 import os
+import struct
 import yaml
 import io
 from datetime import datetime
@@ -15,6 +16,34 @@ from fpdf import FPDF
 app = Flask(__name__)
 app.config['MAX_CONTENT_LENGTH'] = 5 * 1024 * 1024
 CONFIG_FILE = 'druckkalkulation_config.yaml'
+
+
+def image_dimensions(filepath):
+    """Liest Pixelbreite und -hoehe aus PNG/JPEG/WebP ohne externe Libs."""
+    with open(filepath, 'rb') as f:
+        head = f.read(64)
+    if head[:8] == b'\x89PNG\r\n\x1a\n':
+        w, h = struct.unpack('>II', head[16:24])
+        return w, h
+    if head[:2] == b'\xff\xd8':
+        i = 2
+        while i < len(head) - 1:
+            if head[i] != 0xFF:
+                break
+            marker = head[i+1]
+            if marker in (0xC0, 0xC1, 0xC2):
+                h, w = struct.unpack('>HH', head[i+5:i+9])
+                return w, h
+            length = struct.unpack('>H', head[i+2:i+4])[0]
+            i += 2 + length
+    if head[:4] == b'RIFF' and head[8:12] == b'WEBP':
+        if head[12:16] == b'VP8 ':
+            w, h = struct.unpack('<HH', head[26:30])
+            return (w & 0x3FFF) * 2, (h & 0x3FFF) * 2
+        if head[12:16] == b'VP8L':
+            bits = struct.unpack('<I', head[21:25])[0]
+            return (bits & 0x3FFF) + 1, ((bits >> 14) & 0x3FFF) + 1
+    return None, None
 LOGO_FILE = 'static/logo.png'
 
 DEFAULT_VALUES = {
@@ -256,7 +285,11 @@ def invoice_pdf():
     logo_path = os.path.join('static', logo_name) if logo_name else ''
     if logo_name and os.path.exists(logo_path):
         pdf.image(logo_path, x=155, y=8, w=40)
-        logo_bottom = pdf.get_y()
+        img_w, img_h = image_dimensions(logo_path)
+        if img_w and img_h:
+            logo_bottom = 8 + 40 * (img_h / img_w)
+        else:
+            logo_bottom = 8 + 20
     else:
         pdf.set_font("Arial", "B", 18)
         pdf.set_xy(150, 15)