feat: add image render endpoint

This endpoint adds a quick way for clients to request arbitrary image sizes based on the functionality available in the versatileimagefield package.

If we have more advanced use cases we could either take a look at integrating libvips [1] or delegate requests to a thumbor instance [2].

[1] https://github.com/libvips/pyvips [2] https://github.com/thumbor/thumbor

program/models.py

@@ -145,6 +145,18 @@ class Image(models.Model):
     ppoi = PPOIField()
     width = models.PositiveIntegerField(blank=True, null=True)
 
+    def render(self, width: int | None = None, height: int | None = None):
+        if width is None and height is None:
+            return self.image.url
+        elif width and height:
+            return self.image.crop[f"{width}x{height}"].url
+        aspect_ratio = self.width / self.height
+        if width is None:
+            width = int(height * aspect_ratio)
+        if height is None:
+            height = int(width / aspect_ratio)
+        return self.image.thumbnail[f"{width}x{height}"].url
+
     def save(self, *args, **kwargs):
         super().save(*args, **kwargs)