Tune print quality defaults: density 2, font 30pt, threshold 160

- Default density to thick (2) for bolder output
- Default font size to 30pt for better readability
- Add draw.fontmode="1" to disable antialiasing for crisp 1-bit text
- Add ImageOps.autocontrast before thresholding images
- Update web GUI defaults to match CLI

fichero/imaging.py

@@ -2,7 +2,7 @@
 
 import logging
 
-from PIL import Image, ImageDraw, ImageFont
+from PIL import Image, ImageDraw, ImageFont, ImageOps
 
 from fichero.printer import PRINTHEAD_PX
 
@@ -18,6 +18,7 @@ def prepare_image(img: Image.Image, max_rows: int = 240) -> Image.Image:
         log.warning("Image height %dpx exceeds max %dpx, cropping bottom", new_h, max_rows)
         new_h = max_rows
     img = img.resize((PRINTHEAD_PX, new_h), Image.LANCZOS)
+    img = ImageOps.autocontrast(img, cutoff=1)
     img = img.point(lambda x: 1 if x < 128 else 0, "1")
     return img
 
@@ -31,12 +32,13 @@ def image_to_raster(img: Image.Image) -> bytes:
     return img.tobytes()
 
 
-def text_to_image(text: str, font_size: int = 24, label_height: int = 240) -> Image.Image:
-    """Render text in landscape, then rotate 90 degrees for label printing."""
+def text_to_image(text: str, font_size: int = 30, label_height: int = 240) -> Image.Image:
+    """Render crisp 1-bit text, rotated 90 degrees for label printing."""
     canvas_w = label_height
     canvas_h = PRINTHEAD_PX
     img = Image.new("L", (canvas_w, canvas_h), 255)
     draw = ImageDraw.Draw(img)
+    draw.fontmode = "1"  # disable antialiasing - pure 1-bit glyph rendering
 
     font = ImageFont.load_default(size=font_size)