I've rendered a small (couple thousand square) area of my world and it generated a 200mb PNG file that I cannot view nor convert/resize to be viewed. Not sure if I'm missing something, here..?
You probably don't have enough memory to view it; for the same reason Gimp crashed when I tried viewing the image LordHypnos uploaded. Also, MSPaint has trouble opening much smaller images (either "not enough memory or resources" or "invalid file"), even when they take up only a few hundred MB in memory according to Gimp.
As I mentioned before you can get around this by rendering the world in several parts, then resize the generated images and merge them together into a single image (give a few chunks of overlap so you can trim away the edges so they seamlessly fit together); resizing to 50% will reduce the image size by a factor of 4; the largest image I've gotten from a render was around 50 MB in size and could still be opened with Gimp (the world is about 6000x4000 blocks and 60000 chunks).
I also do this to save time; instead of rendering the entire world I only render the areas I've explored since the last time and merge the result with a map of the entire world; for example, this is a rendering of caves I recently explored, and before and after I merged it with the full-size map (resized to 10% of original size):
A better way might be to add an option to produce multiple small tileable images instead of one large image; such a set of images could also be loaded in a viewer which displays them as if they are a single giant image without any of the issues with a single image of the same size (sort of like how Web-based map viewers work), and/or a resize option when rendering (the scale MCMap uses is a bit odd since it renders a single block as 4x4 pixels but for multiple blocks it seems to use 2.828 pixels per block across the image width and 1.414 across the height, as measured after rendering a 1024 block square area 1 block deep).
Also, a small optimization suggestion for MCMap - there appears to be a debug line left in that prints out the locations of every torch found (relative coordinates, not in-world) and when you have a world with a lot (more than a third of a million in my world) it can slow things down, plus the range it checks around each torch is much larger than necessary (torch light only travels 6 blocks before falling below light level 8, and is closer to a circle than a square); I modified MCMap to comment out the torch line and changed the +/- 18 block range (+/- 9 high) around torches to a 6 block circle +/- 4 blocks high, which also makes it much easier to see what caves have actually been explored and reduces surface clutter under forests.
Something I noticed recently is that, when you select not to render the whole world, but only a part of it, the numbers you have to put in are CHUNKS, not coordinates. So when you try to render an area of "a couple thousand of blocks" and you type in from "-2000" to "2000", you actually render the area from the coordinates -32000 to 32000, and it's no wonder that this takes quite a while.
Maybe this misunderstanding solves your problem, The TopMostDog, but if you already figured it out excuse me :-D
Rollback Post to RevisionRollBack
There's a block? Break it. There's a creeper? Slay it. There's a diamond? Get it!
I just tried rendering our world, and MCMap seems to be having a few issues. For simplicity, I copied the server world into the singleplayer save folder so MCMap would find it easily.
1) The big issue is that I've run into is that there are a few areas where it just doesn't render. I'm not exactly sure why, as there is most definitely world there. In some cases, I've even been building there.
2) There are a few areas that are rendering with odd colours: ores on the surface seem to render with a pinky colour, while shallow water and swamps seem to get a purplish-grey colour.
Follow Up: At least in the case of the gash in the picture, it seems MCMap found some data corruption in my world. Given that I copied the data into the SP save and MCMap made the picture from the SP save, I loged into the server and visited the area there and low and behold the server had to generate fresh terrain to fill in that area. Not sure how it came to be glitched, but that's the way of things. Had to replace several regions from backups, and in-game it seems to be in proper condition, so I'm doing another render to see if that fixes things.
I've only had MCMap for a day, and it is already proving useful.