issues: 860625833

Original title: Generating URL for a row inside render_cell hook**

Hey, I am using Datasette to view a database that contains video metadata. It has BLOB columns that contain video thumbnails in JPG format (around 100-500KB per row).

I've registered an output formatter that extends datasette.blob_renderer.render_blob function and serves the column with image/jpeg content type.

```python from datasette.blob_renderer import render_blob

async def render_jpg(datasette, database, rows, columns, request, table, view_name): response = await render_blob(datasette, database, rows, columns, request, table, view_name) response.content_type = "image/jpeg" response.headers["Content-Disposition"] = f'inline; filename="image.jpg"' return response

@hookimpl def register_output_renderer(): return { "extension": "jpg", "render": render_jpg, "can_render": lambda: True, } ```

This works well. I can visit http://localhost:8001/mydb/videos/1.jpg?_blob_column=thumbnail and view the image.

I want to display the image directly with an <img> tag (lazy-loaded of course). So, I need a URL, because embedding base64 would increase the page size too much (each image > 100KB).

Datasette generates a link with .blob extension for blob columns. It does this by calling datasette.urls.row_blob

https://github.com/simonw/datasette/blob/7a2ed9f8a119e220b66d67c7b9e07cbab47b1196/datasette/views/table.py#L169-L179

But I have no way of getting the row inside the render_cell hook.

python @hookimpl def render_cell(value, column, table, database, datasette): if isinstance(value, bytes) and imghdr.what(None, value): # generate url return '$renderedLink'

Any pointers?