Add img_url template tag for legacy use-cases like email

Author: codingjoe

pictures/templatetags/pictures.py

@@ -36,3 +36,29 @@ def picture(field_file, alt=None, ratio=None, container=None, **kwargs):
             "use_placeholders": settings.USE_PLACEHOLDERS,
         }
     )
+
+
+@register.simple_tag()
+def img_url(field_file, file_type, width, ratio=None) -> str:
+    """
+    Return the URL for a specific image file.
+
+    This may be useful for use-cases like emails, where you can't use a picture tag.
+    """
+    try:
+        file_types = field_file.aspect_ratios[ratio]
+    except KeyError as e:
+        raise ValueError(
+            f"Invalid ratio: {ratio}. Choices are: {', '.join(filter(None, field_file.aspect_ratios.keys()))}"
+        ) from e
+    try:
+        sizes = file_types[file_type.upper()]
+    except KeyError as e:
+        raise ValueError(
+            f"Invalid file type: {file_type}. Choices are: {', '.join(file_types.keys())}"
+        ) from e
+    for w, img in sorted(sizes.items()):
+        url = img.url
+        if w >= width:
+            break
+    return url

tests/test_templatetags.py

@@ -1,6 +1,6 @@
 import pytest
 
-from pictures.templatetags.pictures import picture
+from pictures.templatetags.pictures import img_url, picture
 from tests.testapp.models import Profile
 
 picture_html = b"""
@@ -61,3 +61,28 @@ def test_picture__additional_attrs(image_upload_file):
     profile = Profile.objects.create(name="Spiderman", picture=image_upload_file)
     html = picture(profile.picture, ratio="3/2", loading="lazy")
     assert ' loading="lazy"' in html
+
+
+@pytest.mark.django_db
+def test_img_url(image_upload_file):
+    profile = Profile.objects.create(name="Spiderman", picture=image_upload_file)
+    assert (
+        img_url(profile.picture, ratio="3/2", file_type="webp", width=800)
+        == "/_pictures/image/3x2/800w.WEBP"
+    )
+
+
+@pytest.mark.django_db
+def test_img_url__raise_wrong_ratio(image_upload_file):
+    profile = Profile.objects.create(name="Spiderman", picture=image_upload_file)
+    with pytest.raises(ValueError) as e:
+        img_url(profile.picture, ratio="2/3", file_type="webp", width=800)
+    assert "Invalid ratio: 2/3. Choices are: 1/1, 3/2, 16/9" in str(e.value)
+
+
+@pytest.mark.django_db
+def test_img_url__raise_wrong_file_type(image_upload_file):
+    profile = Profile.objects.create(name="Spiderman", picture=image_upload_file)
+    with pytest.raises(ValueError) as e:
+        img_url(profile.picture, ratio="3/2", file_type="gif", width=800)
+    assert "Invalid file type: gif. Choices are: WEBP" in str(e.value)