To compliment the gestures already included, would be neat to be able swipe away images on the built-in image view. Your thumb is already somewhere central from clicking on the image and so would be more fluid to be able to quickly dismiss the image with a brief drag up or down in the image.
I didn’t know this either. I guess the delay is to check if you’re double tapping to Zoom. Personally, I’d still love a swipe gesture to dismiss if the dev agrees.