Django widget to preview images uploaded using a file input

django_form_img_widget.py

from django import forms
from django.utils.safestring import mark_safe

class AdminImageWidget(forms.FileInput):
    """
    A ImageField Widget for admin that shows a thumbnail.
    Taken from https://djangosnippets.org/snippets/1580/
    """

    def __init__(self, attrs={}):
        super(AdminImageWidget, self).__init__(attrs)

    def render(self, name, value, attrs=None):
        output = []
        if value and hasattr(value, "url"):
            output.append(('<a target="_blank" href="%s">'
                           '<img src="%s" style="height: 250px;" /></a> <br /><br />'
                           % (value.url, value.url)))
        output.append(super(AdminImageWidget, self).render(name, value, attrs))
        return mark_safe(u''.join(output))