I made a 32768 × 32768 pixel Mandelbrot png, because it's a fun thing to do.
It renders fine in preview, until I attempt to zoom in (which is the whole point of making the image as big as I made it). 
When I do attempt to zoom in, it starts to grey out the rest of the image, and if I zoom out again, the rest of the image grays out. 
It doesn't ever load. Is there a recommended way that I could render this large image?
[SPECS]
- 2017 15" MBP
- 2.8 GHz Intel Core i7
- 16 GB RAM
- Intel HD Graphics 1536MB
- Radeon Pro 555 2048 MB
- Image format: .png
- Image resolution: 32,768 x 32,768 pixels
- Image file size: 49MB
Best Answer
I would try to open the image in a brand new user account, you can set that up in System Preferences > Users & Groups or just use the Guest account. If you see different results here it must be something in your profile interfering with Preview.
But I'm betting the preview developers didn't account much for people opening 49MB, 32kx32k images. In the likely chance that this is a genuine glitch you could quickly report it at https://www.apple.com/feedback/ or sign up for a developer account & do a full bug report over at https://developer.apple.com/bug-reporting/.
In the short term I would recommend trying to use a different application to view this. A browser or photo editing application might be a good fit. For an image like this there is also a good chance that JPEG would more efficiently compress it & cause less issues, maybe look into converting it with Photoshop or similar.