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<!-- Button to download the image -->
<a href="{{ url_for('download_file', filename='image.png') }}"><button>Download Image</button>
</a>

后端：url_for双大括号即是用来插入变量到模板中的语法。也就是绑定了函数download_file()

python">from flask import Flask, render_template, send_from_directory
@app.route('/download/<filename>')
def download_file(filename):# Send the image file to the clientreturn send_from_directory(app.config['UPLOAD_FOLDER'], filename,as_attachment=True)

Flask Route /download/<filename> : When the button is clicked, it triggers the /download/<filename> route, which uses send_from_directory to serve the image file stored in the static/images directory.