How to Override Django Model\'s Save Method for Selective Image Resizing?

Overriding Django Model's Save Method for Selective Resizing

Question:

How can Django model's save method be overridden to resize an image only when it is added or updated, but not when other fields are edited?

Problem:

The provided code resizes an image every time the model is saved, even if only the description is updated. This is inefficient and unnecessary.

Solution:

The suggested solution involves creating a property that serves as a setter and getter for the image field. This allows tracking changes to the image field and only resizing when it is modified:

<code class="python">class Model(model.Model):
    _image = models.ImageField(upload_to='folder')
    thumb = models.ImageField(upload_to='folder')
    description = models.CharField()

    def set_image(self, val):
        self._image = val
        self._image_changed = True

        # Or put whole logic in here
        small = rescale_image(self.image, width=100, height=100)
        self.image_small = SimpleUploadedFile(name, small_pic)

    def get_image(self):
        return self._image

    image = property(get_image, set_image)

    def save(self, *args, **kwargs):
        if getattr(self, '_image_changed', True):
            small = rescale_image(self.image, width=100, height=100)
            self.image_small = SimpleUploadedFile(name, small_pic)
        super(Model, self).save(*args, **kwargs)</code>

By using this approach, resizing only occurs when the image is added or updated, effectively addressing the concern raised in the original question.

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