A validator image for Wagtail CMS

image_validator.py

import os
from django.core.exceptions import ValidationError
from django.core.files.images import get_image_dimensions
from django.utils.deconstruct import deconstructible
from wagtail.images.models import Image # To get the image object from wagtail collections


@deconstructible
class ImageValidator:
    """ImageField dimensions validator."""
    
    def __init__(self, width=None, height=None,
                 min_width=None, max_width=None,
                 min_height=None, max_height=None,
                 file_path=None, folder_name=None):
        """
        Constructor
        Args:
            width (int): exact width
            height (int): exact height
            min_width (int): minimum width
            min_height (int): minimum height
            max_width (int): maximum width
            max_height (int): maximum height
        """
        self.width = width
        self.height = height
        self.min_width = min_width
        self.max_width = max_width
        self.min_height = min_height
        self.max_height = max_height
        self.file_path = file_path
        self.folder_name = folder_name

    def __call__(self, image):
        img = Image.objects.get(id=image) # Getting the image object from wagtail collections
        
        w, h = get_image_dimensions(img.file)
        ext = os.path.splitext(img.filename)[1]
        valid_extensions = ['.png', '.jpg', '.jpeg']

        if not ext.lower() in valid_extensions:
            raise ValidationError('This file is not a valid image.')

        if self.width is not None and w != self.width:
            raise ValidationError(
                f'({img.filename} - Width: {w}px, Height: {h}px) - '
                f'The width image must be {self.width}px'
            )

        if self.height is not None and h != self.height:
            raise ValidationError(
                f'({img.filename} - Height: {h}px, Width: {w}px) - '
                f'The height image must be {self.height}px '
            )

        if self.min_width is not None and w < self.min_width:
            raise ValidationError(
                f'{img.filename} the min width image must be {self.max_width}px '
            )

        if self.min_height is not None and h < self.min_height:
            raise ValidationError(
                f'{img.filename} the min height image must be {self.height}px '
            )

        if self.max_width is not None and w > self.max_width:
            raise ValidationError(
                f'{img.filename} the max width image must be {self.max_width}px '
            )

        if self.max_height is not None and h > self.max_height:
            raise ValidationError(
                f'{img.filename} the max height image must be {self.max_height}px '
            )

Then import ImageValidator:
`
from django.db import models
from wagtail.core.models import Page
from .image_validator import ImageValidator

class MyPage(Page):
header = models.OneToOneField(
'wagtailimages.Image',
on_delete=models.SET_NULL,
validators=[ImageValidator(width=1370, height=385)], # Set the params to validation!
related_name='main_image'
)

`

Thanks a lot for this, I'll try it out

Seems to work..
You might want to change min_width and min_height validation message to this:

        if self.min_width is not None and w < self.min_width:
            raise ValidationError(
                f'{img.filename} the min width image must be {self.min_width}px '
            )

        if self.min_height is not None and h < self.min_height:
            raise ValidationError(
                f'{img.filename} the min height image must be {self.min_height}px '
            )

@ag-castro, why not support gif?

I really appreciate this script. Just exactly what I needed. Cheers mate

How would this work in a model that extends AbstractImage?