slide updates for watermark

Author: aamini

scripts/png_to_pdf.py

@@ -6,10 +6,12 @@
 from tqdm import tqdm
 import cv2
 import numpy as np
+import tempfile
 
 parser = argparse.ArgumentParser()
 parser.add_argument("-i", "--input", help="input directory with pngs")
 parser.add_argument("-o", "--output", help="output pdf file")
+parser.add_argument("--quality", type=int, default=40, help="quality of the images")
 parser.add_argument("--no-watermark", action='store_true', help="dont include a watermark")
 args = parser.parse_args()
 
@@ -34,14 +36,51 @@
 pdf.set_author("A. Amini, A.P. Amini. MIT 6.S191")
 pdf.set_margins(0, 0, 0)
 
+if not args.no_watermark:
+    # Get the directory where this script is located
+    script_dir = os.path.dirname(os.path.abspath(__file__))
+    watermark_path = os.path.join(script_dir, "watermark.png")
+    watermark_rgba = cv2.imread(watermark_path, cv2.IMREAD_UNCHANGED)
+    if watermark_rgba is None:
+        raise FileNotFoundError(f"Could not load watermark from {watermark_path}")
+    
+    # Extract alpha channel (we'll use this as the watermark pattern)
+    if watermark_rgba.shape[2] == 4:
+        watermark_alpha = watermark_rgba[:, :, 3]
+    else:
+        # If no alpha channel, use grayscale as pattern
+        watermark_alpha = cv2.cvtColor(watermark_rgba, cv2.COLOR_BGR2GRAY)
+
 # imagelist is the list with all image filenames
 files = sorted(glob.glob(os.path.join(args.input, "*.jpeg")))
 files.sort(key=lambda var:[int(x) if x.isdigit() else x for x in re.findall(r'[^0-9]|[0-9]+', var)])
 import pdb; pdb.set_trace()
 for image in tqdm(files):
     pdf.add_page()
-    pdf.image(image, x=0, y=0, w=1280, h=720)
+    image_data = cv2.imread(image)
+
     if not args.no_watermark:
-        pdf.image("watermark.png", x=0, y=0, w=1280, h=720)
+        # Calculate median brightness of the slide (normalized to 0-1)
+        gray_slide = cv2.cvtColor(image_data, cv2.COLOR_BGR2GRAY)
+        median_brightness = np.median(gray_slide) / 255.0
+        
+        # Resize watermark alpha to match the slide dimensions
+        watermark_resized = cv2.resize(watermark_alpha, (image_data.shape[1], image_data.shape[0]))
+        
+        # Choose watermark color based on slide brightness
+        if median_brightness < 0.5:
+            # Dark slide -> add white watermark
+            watermark_color = cv2.cvtColor(watermark_resized, cv2.COLOR_GRAY2BGR)
+            image_data = cv2.addWeighted(image_data, 1, watermark_color, 1.2, 0)
+        else:
+            # Light slide -> subtract black watermark
+            watermark_color = cv2.cvtColor(watermark_resized, cv2.COLOR_GRAY2BGR)
+            # Subtract the watermark (makes it darker where watermark exists)
+            image_data = cv2.subtract(image_data, (watermark_color * 1.2).astype(np.uint8))
+
+    temp_file = tempfile.mktemp() + ".jpg"
+    cv2.imwrite(temp_file, image_data, [int(cv2.IMWRITE_JPEG_QUALITY), args.quality])
+    pdf.image(temp_file, x=0, y=0, w=1280, h=720)
+    os.remove(temp_file)
 
 pdf.output(args.output, "F")