在Symfony2中上传文件时设置文件类型

So I have the file upload working well. However I need to set type of file that is allowed, where and how do I set the type of file that can be uploaded. It's supposed to be an image file, and I don't want users (obviously) uploading anything but an image. I would assume it's somewhere in validation.yml?

Thank you!

There are two ways, or using the file validation attribute, or the image validation attribute, this last as the accepted mime types as image/*

The examples on the site goes as followed:

# src/Acme/BlogBundle/Resources/config/validation.yml
Acme\BlogBundle\Entity\Author:
    properties:
        bioFile:
            - File:
                maxSize: 1024k
                mimeTypes: [application/pdf, application/x-pdf]
                mimeTypesMessage: Please upload a valid PDF

# src/Acme/BlogBundle/Resources/config/validation.yml
Acme\BlogBundle\Entity\Author
    properties:
        headshot:
            - Image:
                minWidth: 200
                maxWidth: 400
                minHeight: 200
                maxHeight: 400