The built-in gallery refuses to load a 7500x5000 jpg. What's the best way of opening this? (I'd rather avoid decreasing the resolution to keep readability)

I used to use the Opera Mobile browser on N9 to view huge jpg maps of my entire region. When you first open the image file in Opera, it's sized to fit the screen. Click on the image again to view in full resolution. Works surprising well. It's the only app I found that could view those image files fully. No longer have those files now, so not really sure of the image size limit for Opera Mobile, but they are much bigger than what you have.

I have since migrated those jpg maps to CloudGPS which is more suitable, not to mention faster for viewing my map, making it my most loved N9 app. There is no size limit in CloudGPS since the maps are composed from tiny jpg, but the map conversion process is very tedious for my use case as I want to use the GPS with it.