How to Validate Rectangular Images in Django Using Python

When handling image uploads in a Django project, there may be situations where you need to enforce specific dimensions, such as ensuring that the uploaded image is a rectangle (rather than a square). This is especially useful for profile headers, banners, or media that requires a non-square format.

In this article, we will use Django’s validation system and Pillow library.

Prerequisites

Before implementing this solution, make sure you have the following dependencies installed:

1. Django (for web framework functionality)
2. Pillow (for image processing)

If you don’t have Pillow installed, you can add it using the following command:

python -m pip install pillow

Write a validator

In order to verify that the uploaded image is a rectangle, we need to check width and high image. If both dimensions are equal, it means the image is a square and we will throw a validation error.

Here is the code for the custom validator:

from django.core.exceptions import ValidationError
from PIL import Image

def validate_rectangular_image(image):
    """
    Validator to ensure an uploaded image is rectangular and not square.
    """
    image = Image.open(image)  # Open the uploaded image using Pillow
    width, height = image.size  # Extract dimensions

    if width == height:  # Check if image is square
        raise ValidationError("Uploaded image must be rectangular (not square).")

    return image

Integrate validators with Django models

To use this validator in a Django application, you can add it to a model field. For example, let’s say you have an ImageField in your user profile banner’s model:

from django.db import models
from .validators import validate_rectangular_image  # Import the custom validator

class Profile(models.Model):
    name = models.CharField(max_length=100)
    banner_image = models.ImageField(
        upload_to='banners/', 
        validators=[validate_rectangular_image],
        help_text="Please upload a rectangular image for the banner."
    )

    def __str__(self):
        return self.name

How it works:

• this validate_rectangular_image This function will be called whenever a file is uploaded banner_image site.
• If the image is square, then ValidationError Raised, preventing the file from being saved.
• Only rectangular images will pass validation and be uploaded successfully.

Handling validation errors in forms

If you use Django forms for image uploads, an error will be displayed to the user when they submit an invalid image.

For example, a simple form might look like this:

from django import forms
from .models import Profile

class ProfileForm(forms.ModelForm):
    class Meta:
        model = Profile
        fields = ['name', 'banner_image']

When users upload a square image, they see the error message:

“Uploaded images must be rectangular (not square).”

test validator

You can try uploading square and rectangular images to test the feature.

1. Square image (for example, 300×300):
   The validator will reject the profile and propose ValidationError.

2. Rectangular image (for example, 400×300):
   The file will be accepted by the validator and the image will be uploaded successfully.

final notes

By using this approach, you can seamlessly enforce image size requirements in your Django applications. this Pillow The library can easily handle image sizes, and Django’s validation system lets you easily integrate custom logic.

Key points:

• Use Pillow to extract image dimensions.
• Increase ValidationError When an uploaded image does not meet your standards.
• Integrate validators into Django models to ensure data integrity.

By combining Django and Pillow, you can create powerful and flexible image upload rules to improve the quality of your web applications.

Happy coding! 🚀