图像处理脚本：PNG转换器和resizer

<code class="python">from PIL import Image
import os

def ensure_transparency(image):
    """Ensures the image has transparency; replaces white backgrounds with transparency."""
    if image.mode != 'RGBA':
        image = image.convert('RGBA')
    if image.getchannel('A').getextrema()[0] != 0:
        data = image.getdata()
        new_data = [(r, g, b, 0) if r > 240 and g > 240 and b > 240 else (r, g, b, a) for r, g, b, a in data]
        image.putdata(new_data)
    return image

def crop_and_resize(image, target_width, target_height):
    """Crops unused space and resizes to the target dimensions, maintaining aspect ratio."""
    bbox = image.getbbox()
    if bbox is None:
        return None  # Image is empty or fully transparent

    cropped = image.crop(bbox)
    width, height = cropped.size
    aspect_ratio = target_width / target_height

    if width / height > aspect_ratio:
        new_width = target_width
        new_height = int(new_width * (height / width))
    else:
        new_height = target_height
        new_width = int(new_height * (width / height))

    resized = cropped.resize((new_width, new_height), Image.LANCZOS)
    return resized

def process_image(input_path, output_path, target_width, target_height):
    """Processes a single image: ensures transparency, crops, resizes, and saves."""
    try:
        image = Image.open(input_path)
        image = ensure_transparency(image)
        resized_image = crop_and_resize(image, target_width, target_height)
        if resized_image:
            canvas = Image.new("RGBA", (target_width, target_height), (255, 255, 255, 0))
            x_offset = (target_width - resized_image.width) // 2
            y_offset = (target_height - resized_image.height) // 2
            canvas.paste(resized_image, (x_offset, y_offset))
            canvas.save(output_path, "PNG")
            return True
        else:
            return False
    except IOError:
        print(f"Error processing {input_path}")
        return False

def shorten_filename(filename, max_length=30):
    """Shortens filenames, preserving extensions."""
    name, ext = os.path.splitext(filename)
    return f"{name[:max_length]}{ext}"

def batch_process_images(input_dir, output_dir, target_width, target_height):
    """Processes all images in the input directory."""
    os.makedirs(output_dir, exist_ok=True)
    skipped = []
    for filename in os.listdir(input_dir):
        if filename.lower().endswith(('.jpg', '.jpeg', '.png')):
            input_path = os.path.join(input_dir, filename)
            new_filename = shorten_filename(filename.replace(" ", "_"))
            output_path = os.path.join(output_dir, new_filename)
            if not process_image(input_path, output_path, target_width, target_height):
                skipped.append(filename)
    if skipped:
        print("\nSkipped images:")
        for filename in skipped:
            print(f"- {filename}")


input_directory = './images'
output_directory = './edited_images'
batch_process_images(input_directory, output_directory, 400, 200) #Example 2:1 ratio</code>