perf: optimize PNG compression only on final operations

- Add is_final parameter to trim_whitespace and convert_to_monochrome
- Only optimize PNGs on the final operation of each level
- Remove optimization from extract command
- Level 1: optimize in trim_whitespace
- Level 2: optimize in convert_to_monochrome
- Level 3: defer to optipng

pdf_cleaner.py

@@ -81,13 +81,14 @@ def extract(input_pdf):
     
     print(f"Extracted {len(pages)} pages to {temp_dir}/")
 
-def trim_whitespace(image_path: str) -> bool:
+def trim_whitespace(image_path: str, is_final: bool = False) -> bool:
     """Remove white space from around the image.
     
     Handles both RGB and RGBA images, treating transparent pixels as white.
     
     Args:
         image_path: Path to the image file
+        is_final: Whether this is the final operation on the image
     
     Returns:
         bool: True if successful, False otherwise
@@ -124,8 +125,8 @@ def trim_whitespace(image_path: str) -> bool:
         # Crop the original image (preserving transparency)
         cropped = image.crop((x1, y1, x2, y2))
         
-        # Save the cropped image
+        # Save the cropped image, optimizing only if this is the final operation
-        cropped.save(image_path, "PNG", optimize=False)
+        cropped.save(image_path, "PNG", optimize=is_final)
         return True
         
     except Exception as e:
@@ -206,11 +207,15 @@ def deskew():
         else:
             print("  No line segments detected")
 
-def convert_to_monochrome(image_path: str) -> bool:
+def convert_to_monochrome(image_path: str, is_final: bool = False) -> bool:
     """Convert image to 1-bit monochrome.
     
     Handles RGBA images by converting transparent pixels to white before thresholding.
     
+    Args:
+        image_path: Path to the image file
+        is_final: Whether this is the final operation on the image
+    
     Returns:
         bool: True if successful, False otherwise
     """
@@ -243,8 +248,8 @@ def convert_to_monochrome(image_path: str) -> bool:
         # Convert to 1-bit using threshold
         image = image.point(lambda x: 255 if x > settings.MONOCHROME_THRESHOLD else 0, '1')
         
-        # Save the monochrome image
+        # Save the monochrome image, optimizing only if this is the final operation
-        image.save(image_path, "PNG", optimize=False)
+        image.save(image_path, "PNG", optimize=is_final)
         return True
         
     except Exception as e:
@@ -312,7 +317,8 @@ def optimize(level):
     print("\nTrimming whitespace from images...")
     for i, file_path in enumerate(temp_files, 1):
         print(f"[{i}/{total_files}] Processing {os.path.basename(file_path)}...", end='', flush=True)
-        if trim_whitespace(file_path):
+        # Only optimize if this is the final step (level 1)
+        if trim_whitespace(file_path, is_final=(opt_level == OptimizationLevel.TRIM)):
             successful['trim'] += 1
             print(" ")
         else:
@@ -323,7 +329,8 @@ def optimize(level):
         print("\nConverting to monochrome...")
         for i, file_path in enumerate(temp_files, 1):
             print(f"[{i}/{total_files}] Converting {os.path.basename(file_path)}...", end='', flush=True)
-            if convert_to_monochrome(file_path):
+            # Only optimize if this is the final step (level 2)
+            if convert_to_monochrome(file_path, is_final=(opt_level == OptimizationLevel.MONOCHROME)):
                 successful['monochrome'] += 1
                 print(" ")
             else: