Images Resizing

I'm trying to upload a hi-res (5079x3189) map for my game, still under the 10mb size limit, but no matter what I do it comes out blurry. It seems like Roll20 resizes uploads to a much lower resolution no matter how you scale them afterward. Clicking the map and hitting Z gives me the original image in a popup, which is noticeably higher-quality and crisper. Problem is, why can't this be a feature for the tabletop space itself? For stuff like maps I want everything to be as high-res as possible.

Roll20 seems to make multiple versions of your file on upload. It then uses one appropriate to your zoom level. Sometimes it has trouble loading the high-res version and loads a low-res/thumbnail version first. Changing zoom level, Ctrl+F5 to do a hard browser refresh, or clearing the browser cache can help get a second try at loading the higher-res version.

Piggybacking on Brian's reply, I have a higher res world map (though less than your example) that takes a while to load fully, sometimes up to 10-20 seconds(?). The low-res version pops up immediately so we don't have to watch it load, partying like's it's 1993. 

If I have a page that has a very large map (typically a city or world), I will frequently uploaded it in slices--6 or 8 chunks which I position in the map page to look seamless. I will also produce an extremely low res version (like 5-10 pixels per unite) of the whole thing and place in register behind the entire map. This achieves several things: The low res composite map is the largest image on the page and gets used for the thumbnail on the page tab, which makes it easier to identify. Immediately upon load the blurry low res map fills the screen and begins being replaced by the hi res chunks. This gives the players instant feedback that the image is loading and orients them while the full res images finalize. At some magnifications, the seams between chunks can show (just the way "zooming" works--it's averaging pixels). Having the simple low res version behind disguises those seams.

Jay I would like to take a look, if you want to send me an invite for your game that has this map. I have experiemented often with large maps, the largest I could get to work (without tiling / slicing) was about 7500x7500 pixels. Best performance (better) tend to occur on 5000x5000 or smaller. Are you setting your map diminsions in roll20 to the exact Native resolution 5079x3189? (Under right click > advanced > Set Diminsions > Pixels)? If yes, are you then viewing the map PAGE at 100% zoom level, and try 90%?  (We will not be surprised to see lowering quality at 200%, 250% zooms). If yes, are you then waiting "long enough" for the image to snap into focus? Roll20 will load a low-res, partial-image first, but after a matter of seconds (say up to 1-3 minutes) the image should finish loading to display full resolution. To get a fresh start, clear your browser's cache "Clear Cache" and load the page again (on 100% zoom and wait 3 minutes). I like keith's suggestions, and those power-user clever techniques could help, BUT those should not be necessary, as basic default Roll20 is designed to be able to show your map image at good resolution at 100% zoom after it finishes loading unless there's a problem.

Ctrl+F5'ing, or sticking to 100% zoom, mostly fixes the problem.