如何在Django Admin中上传图片前检查图片宽高？

To validate the aspect ratio of images before uploading in your Django Admin, you have two main approaches—model-level validation (runs everywhere the model is saved) or admin form-level validation (only applies to the admin interface). Here's how to implement both:

Prerequisite: Install Pillow #

First, you need the Pillow library to process image dimensions. Install it via pip:

pip install pillow

Approach 1: Model-Level Validation (Recommended) #

This method ensures the aspect ratio check runs whenever the Banner model is saved—whether via admin, API, or any other form. Modify your Banner model to add a clean() method:

from django.db import models
from django.core.exceptions import ValidationError
from PIL import Image
from django.utils.translation import gettext_lazy as _

class Banner(models.Model):
    image = models.ImageField(
        _('Image'), upload_to=upload_path, blank=True, null=True,
        content_types=['image/jpg', 'image/jpeg', 'image/png'],
        max_size=1 * 1024 * 1024, extensions=['jpg', 'jpeg', 'png']
    )
    type_of_banner = models.CharField(_('Type of Banner'), max_length=3, default='web')
    
    class Meta:
        verbose_name = _('Banner')
        verbose_name_plural = _('Banners')
    
    def __str__(self):
        return '%s' % str(self.id)
    
    def clean(self):
        super().clean()
        
        # Only validate if an image is provided
        if self.image:
            try:
                # Open the uploaded image to get dimensions
                with Image.open(self.image) as img:
                    width, height = img.size
                    
                    # Define your required aspect ratio (adjust to your needs)
                    REQUIRED_ASPECT_RATIO = 16 / 9  # Example: 16:9 landscape
                    # Allow a small tolerance to account for minor pixel differences
                    TOLERANCE = 0.01
                    
                    current_ratio = width / height
                    
                    # Check if the ratio is within acceptable range
                    if abs(current_ratio - REQUIRED_ASPECT_RATIO) > TOLERANCE:
                        raise ValidationError({
                            'image': _(
                                "Image must have an aspect ratio of 16:9. "
                                "Current dimensions are %(width)dx%(height)d (ratio: %(ratio).2f:1)."
                            ) % {
                                'width': width,
                                'height': height,
                                'ratio': current_ratio
                            }
                        })
            except Exception as e:
                # Handle invalid image files
                raise ValidationError({
                    'image': _("Invalid image file: %(error)s") % {'error': str(e)}
                })

Why this works: #

• The clean() method is called automatically before the model is saved, so invalid images are rejected before being stored on the server.
• This validation applies to all instances of the Banner model, not just those created via admin.

Approach 2: Admin Form-Level Validation #

If you only want the aspect ratio check to apply in the Admin interface (and not elsewhere like APIs), create a custom ModelForm for your BannerAdmin:

from django.contrib import admin
from django import forms
from django.core.exceptions import ValidationError
from PIL import Image
from django.utils.translation import gettext_lazy as _
from .models import Banner

class BannerAdminForm(forms.ModelForm):
    class Meta:
        model = Banner
        fields = ('image', 'type_of_banner')
    
    def clean_image(self):
        image = self.cleaned_data.get('image')
        
        if image:
            try:
                with Image.open(image) as img:
                    width, height = img.size
                    
                    REQUIRED_ASPECT_RATIO = 16 / 9  # Adjust to your needs
                    TOLERANCE = 0.01
                    current_ratio = width / height
                    
                    if abs(current_ratio - REQUIRED_ASPECT_RATIO) > TOLERANCE:
                        raise ValidationError(
                            _(
                                "Image must have an aspect ratio of 16:9. "
                                "Current dimensions are %(width)dx%(height)d (ratio: %(ratio).2f:1)."
                            ) % {
                                'width': width,
                                'height': height,
                                'ratio': current_ratio
                            }
                        )
            except Exception as e:
                raise ValidationError(_("Invalid image file: %(error)s") % {'error': str(e)})
        
        return image

class BannerAdmin(admin.ModelAdmin):
    model = Banner
    form = BannerAdminForm  # Attach the custom form
    fields = ('image', 'type_of_banner')
    list_display = ('image', 'type_of_banner')

# Register the admin as before
android_dashboard.register(Banner, BannerAdmin)

Key Notes: #

• Adjust REQUIRED_ASPECT_RATIO to match your needs (e.g., 1.0 for square images, 9/16 for portrait).
• The TOLERANCE value prevents rejecting images with minor pixel differences (e.g., a 1600x901 image instead of 1600x900).
• Both methods will display a clear error message in the Admin interface if the image doesn't meet the ratio requirement, before saving the file to the server.

内容的提问来源于stack exchange，提问作者Alireza