mailc/image_processor.py

from PIL import Image
import os
from config import Config
from logger import logger

class ImageProcessor:
    # 格式映射：将常见的小写格式名转换为 Pillow 可识别的格式名
    FORMAT_MAP = {
        'jpg': 'JPEG',
        'jpeg': 'JPEG',
        'png': 'PNG',
        'webp': 'WEBP',
        'gif': 'GIF',
        'bmp': 'BMP',
        'tiff': 'TIFF',
    }

    @staticmethod
    def resize_by_ratio(img, ratio_width, ratio_height):
        """等比例缩放至目标比例（最长边适配）"""
        w, h = img.size
        target_ratio = ratio_width / ratio_height
        current_ratio = w / h
        if current_ratio > target_ratio:
            new_w = int(h * target_ratio)
            new_h = h
        else:
            new_w = w
            new_h = int(w / target_ratio)
        return img.resize((new_w, new_h), Image.Resampling.LANCZOS)

    @staticmethod
    def resize_by_pixel(img, target_width, target_height):
        """等比例缩放至不超过目标像素（保持比例，以较长边为准）"""
        w, h = img.size
        ratio_w = target_width / w
        ratio_h = target_height / h
        ratio = min(ratio_w, ratio_h)
        new_w = int(w * ratio)
        new_h = int(h * ratio)
        return img.resize((new_w, new_h), Image.Resampling.LANCZOS)

    @staticmethod
    def convert_image(input_path, output_path, target_format, quality=None):
        """
        转换图片格式
        target_format: 小写字符串，如 'jpg', 'png', 'webp'
        """
        try:
            with Image.open(input_path) as img:
                # 获取 Pillow 标准格式名
                pillow_format = ImageProcessor.FORMAT_MAP.get(target_format.lower())
                if pillow_format is None:
                    logger.error(f"不支持的输出格式: {target_format}")
                    return False

                # 对于 JPEG 格式，需要处理透明通道
                if pillow_format == 'JPEG' and img.mode in ('RGBA', 'P'):
                    rgb_img = Image.new('RGB', img.size, (255, 255, 255))
                    rgb_img.paste(img, mask=img.split()[-1] if img.mode == 'RGBA' else None)
                    img = rgb_img

                save_kwargs = {}
                if pillow_format in ('JPEG', 'WEBP'):
                    save_kwargs['quality'] = quality if quality is not None else Config.DEFAULT_QUALITY
                elif pillow_format == 'PNG':
                    save_kwargs['compress_level'] = 6

                img.save(output_path, format=pillow_format, **save_kwargs)
                logger.info(f"转换成功: {input_path} -> {output_path}")
                return True
        except Exception as e:
            logger.error(f"转换失败 {input_path}: {e}")
            return False