Method to_python

django/forms/fields.py:722–763

Check that the file-upload field data contains a valid image (GIF, JPG, PNG, etc. -- whatever Pillow supports).

(self, data)

    }

    def to_python(self, data):
        """
        Check that the file-upload field data contains a valid image (GIF, JPG,
        PNG, etc. -- whatever Pillow supports).
        """
        f = super().to_python(data)
        if f is None:
            return None

        from PIL import Image

        # We need to get a file object for Pillow. We might have a path or we
        # might have to read the data into memory.
        if hasattr(data, "temporary_file_path"):
            file = data.temporary_file_path()
        else:
            if hasattr(data, "read"):
                file = BytesIO(data.read())
            else:
                file = BytesIO(data["content"])

        try:
            # load() could spot a truncated JPEG, but it loads the entire
            # image in memory, which is a DoS vector. See #3848 and #18520.
            image = Image.open(file)
            # verify() must be called immediately after the constructor.
            image.verify()

            # Annotating so subclasses can reuse it for their own validation
            f.image = image
            # Pillow doesn't detect the MIME type of all formats. In those
            # cases, content_type will be None.
            f.content_type = Image.MIME.get(image.format)
        except Exception as exc:
            # Pillow doesn't recognize it as an image.
            raise ValidationError(
                self.error_messages["invalid_image"],
                code="invalid_image",
            ) from exc
        if hasattr(f, "seek") and callable(f.seek):
            f.seek(0)
        return f

    def widget_attrs(self, widget):
        attrs = super().widget_attrs(widget)