User-generated fields in Django - django

Question

I'm building a Djano application which displays a set of images, and a form for each image for recording specific image characteristics. The user initializes a "project", where they specify the set of images that will be displayed for assessment. At project initialization, I'd like to give the user the ability to add custom boolean fields (i.e. a set of checkboxes), but I can't figure out how to build the database models.
For example, a user might initialize my_project with image_A.png, image_B.png and image_C.png for assessment. The default form they'll get for each image lets them choose between PASS, FAIL and UNKNOWN. They might wish to add custom fields like "poorly cropped", "over-exposed" or "blurry" (the idea being that the image could be a global PASS, but small failures, specific to the context of this image set, could still be recorded).
Generally, I'm trying to come up with a way to model user-generated fields in Django.

Answer 1

If I correctly understand, you don't need dynamic model fields, instead you can add model, which contains specific attributes for image in project, something like:
class Image(models.Model):
name = models.CharField()
img = models.ImageField()
class ProjectImage(models.Model):
image = models.ForeignKey('Image')
project = models.ForeignKey('Project')
flag = models.CharField(choices=PASS_FAIL_UNKNOWN)
class ProjectImageTag(models.Model):
project_image = models.ForeignKey(ProjectImage)
value = models.CharField()
class Project(models.Model):
images = models.ManyToManyField('Image', through=ProjectImage)
Also, you can store such tags in json field or postgres hstore field instead of separate table.
EDIT
Variation with predefined keys:
class ProjectImage(models.Model):
image = models.ForeignKey('Image')
project = models.ForeignKey('Project')
flag = models.CharField(choices=PASS_FAIL_UNKNOWN)
class Image(models.Model):
name = models.CharField()
img = models.ImageField()
class Project(models.Model):
images = models.ManyToManyField('Image', through=ProjectImage)
class ProjectImageParams(models.Model):
project_image = models.ForeignKey(ProjectImage, related_name='params')
key = models.CharField()
value = models.BooleanField()
Params of image may be obtained with ProjectImage().params.all(). And yes, django-eav may be a good option.