Python利用PIL库实现图片转Base64字符串的完整指南

pip install pillow

from PIL import Image
import base64
from io import BytesIO

def image_to_base64(image_path, format='PNG'):
    """
    将图像文件转换为Base64字符串
    
    参数:
        image_path: 图像文件路径
        format: 输出格式(如'PNG', 'JPEG')，默认为PNG
    
    返回:
        Base64编码字符串
    """
    with Image.open(image_path) as img:
        # 创建字节流缓冲区
        buffered = BytesIO()
        # 将图像保存到缓冲区，指定格式
        img.save(buffered, format=format)
        # 获取缓冲区内容并编码为Base64
        base64_str = base64.b64encode(buffered.getvalue()).decode('utf-8')
    return base64_str

# 使用示例
base64_str = image_to_base64('example.jpg')
print(base64_str[:100] + "...")  # 打印前100个字符

def pil_image_to_base64(pil_img, format='PNG'):
    buffered = BytesIO()
    pil_img.save(buffered, format=format)
    return base64.b64encode(buffered.getvalue()).decode('utf-8')

# 使用示例
img = Image.open('example.jpg')
base64_str = pil_image_to_base64(img)

def image_to_data_uri(image_path, format='PNG'):
    base64_str = image_to_base64(image_path, format)
    return f"data:image/{format.lower()};base64,{base64_str}"

# HTML中使用示例
html_img_tag = f'<img src="{image_to_data_uri('example.jpg')}">'

# JPEG格式（有损压缩，文件更小）
jpeg_base64 = image_to_base64('photo.jpg', 'JPEG')

# GIF格式（支持动画）
gif_base64 = image_to_base64('animation.gif', 'GIF')

# WEBP格式（现代高效格式）
webp_base64 = image_to_base64('image.webp', 'WEBP')

def image_to_base64_with_quality(image_path, format='JPEG', quality=85):
    with Image.open(image_path) as img:
        buffered = BytesIO()
        img.save(buffered, format=format, quality=quality)
        return base64.b64encode(buffered.getvalue()).decode('utf-8')

# 使用示例（50%质量的JPEG）
low_quality_base64 = image_to_base64_with_quality('photo.jpg', 'JPEG', 50)

def base64_to_image(base64_str, output_path=None):
    """
    将Base64字符串转换回图像文件
    
    参数:
        base64_str: Base64编码字符串
        output_path: 可选，保存路径。如果不提供则返回PIL图像对象
    """
    image_data = base64.b64decode(base64_str)
    img = Image.open(BytesIO(image_data))
    
    if output_path:
        img.save(output_path)
        print(f"图像已保存到 {output_path}")
    else:
        return img

# 使用示例
base64_str = image_to_base64('example.jpg')
base64_to_image(base64_str, 'restored.jpg')

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/convert', methods=['POST'])
def convert_to_base64():
    if 'file' not in request.files:
        return jsonify({'error': 'No file uploaded'}), 400
    
    file = request.files['file']
    if file.filename == '':
        return jsonify({'error': 'Empty filename'}), 400
    
    try:
        # 将上传的文件转为PIL图像
        img = Image.open(file.stream)
        
        # 转换为Base64（这里使用PNG格式）
        base64_str = pil_image_to_base64(img)
        
        return jsonify({
            'base64': base64_str,
            'data_uri': image_to_data_uri(file.stream, 'PNG')
        })
    except Exception as e:
        return jsonify({'error': str(e)}), 500

if __name__ == '__main__':
    app.run(debug=True)