Increase the rendered "single product image" size

I would like the product image on the product page to be larger, and I changed the page layout to accommodate this. (In content-single-product.php, I increased the number of columns of the div that contains the image to 9 and decreased the number of columns of the adjacent div to 3.) The image seems locked in a 458 x 458 pixel frame. Changing the settings in WooCommerce > Settings > Products > Product Image Sizes does nothing, even after regenerating the thumbnails.

Below is a screenshot of the issue:

https://i58.tinypic.com/zstziu.jpg

The image is 800 x 531 pixels but it is being cropped in the 458 x 458 frame.

Thanks so much!!