Download image from html Canvas element in macOS Safari?

Websites such as this one use the HTML canvas element to display images. https://digital.gonzaga.edu/digital/collection/p16011coll4/id/93/rec/5 The Safari Web Inspector's Graphics tab shows cut-up tiles of the image that can be saved independently. But doesn't give the full-res combined image. I want to save the image from the canvas, not via an alternative method. [Sometimes](https://oregondigital.org/concern/images/df70cx57n) websites like this have a "download" link, but in this case it does not. Inspecting the source [shows a low-res image used in the preview thumbnail](https://digital.gonzaga.edu/digital/api/singleitem/image/p16011coll4/93/default.jpg) but the canvas appears to load a different, higher-resolution version of the image. Ideally could be done from the macOS Safari Web Inspector. I would also be interested in any Safari Extensions that enable this functionality. How can I get/export/download the full-resolution combined image being displayed by this canvas element?