Thursday, March 10, 2011

In Which Telecanter Learns About DPI and Weeps

Yeah, I love those old time chapter headings too.  And, okay, I didn't weep, but I was pretty discouraged for a few minutes.  So, I've heard about DPI, I know about compression, about resolution, but I never had to take something I'd messed with on the web and try to blow it up.

On I would download the largest jpg they would let me work with.  But when I wanted to blow my map to 18x24, it was a no go.  The guy at the shop told me he needed closer to 300 DPI and my pic was 70 something.

Luckily it worked out okay for my session because the 11x11 that I had printed up looked like a legit scroll.  But, now I'm thinking of doing all map work in svg.  I have Inkscape and will try to learn it.  It looks like I can embed a bitmap in a svg file and it will scale it with some aliasing.  Any of you digital wizards want to weigh in with your experience/suggestions?


  1. Um . . . hmm. Well, I just make sure any image I am working with is at least 300 dpi. If it is a map and I want to zoom in on a particular piece, I crop the bit I want to focus on, then print it out. I then place the print out under a sheet of paper, trace, then fill in the extra zoomed in details, then scan it back in.

    I start out a lot of stuff on paper anyway, then scan it in to add the finishing touches and color. I'm always flopping back and forth between digital and paper, so it is just second nature. Perhaps it's not efficient - but I enjoy it.

    Oh, and I've tried vector - but that just ends up to be a pain in the ass for me. is fine for most stuff - and Adobe photoshop for fancy-shmancy stuff.

    - Ark

  2. Before you jump into Inkscape/SVG, talk to your printer and find out what specific formats they require.

    If your map is basically 'black on white', you might consider handling a large 300 dpi bitmap image but limit the 'mode' of the image to greyscale - much less data for software to have to wrestle with.

    If you do go the Inkscape route, make sure to test the output of Inkscape with your printer's required file format(s). Working with vector graphics can eat up hours...

  3. Print it in whatever res you got on whatever paper.

    Then dunk the printout in water for a few minutes, then hang it up to dry.

    Voila! instant old map.

  4. Buttering and baking will also work, and you might be able to combine them once it's dry. Just don't do this on the rack of the oven, or you'll get lines on the paper. Obviously, you don't want to heat it too hot either, or it'll burn (You shouldn't have problems with this - I'm just making sure no-one tries to sue me or something if they aren't careful about it). If you want it to look like it's been through a fire, hold a match under it in the desired location. This will brown the paper, and set it on fire a bit after that. To combine the two, I'd guess that you butter it after, as lighting oil soaked paper that you're holding doesn't sound like a great idea.

    Side note: Zak's method should not be used with graph paper, as it will (?) cause the ink to run. No clue about whether or not the butter will though, as I haven't tried it on that kind of paper.

  5. If you're going the Inkscape route, you'll find a handy tool under the Path-menu: "Trace Bitmap..."
    Just import/drag your map into Inkscape, select it, then use "Trace Bitmap" and voila - you have a vectorised version of your image!

    I just did a quick test on your original brown map and it worked fine. The result is here (ZIP-archive, 7 MB). There's one version with a paper background and everything, and one with just the traced map (black and white). Both in 300 DPI.

    Another good use of this is to first hand draw your map, scan it, and then vectorise it. It will keep your "style" but still be in a very printer-friendly version (Inkscape can export to PDF)!

  6. I'm an old photoshop head and have never invested the time with vector programs to get comfortable with them. I tend to hand draw and scan, per Arkhein. That said, most computers these days will deal comfortably with seriously big bitmap files even in full color.

    Trying to clean up a low-res map for high-res on the computer is the sort of idiotic time sink I fall into much too often. Any of these other suggestions is much better.

  7. ...BTW, I've known a bunch of professional graphic artists who knew nothing about DPI, nor even, after a traumatic experience like yours, were ever able to design for specific resolutions beyond just setting the "dpi" pane in photoshop's image size window. It's a surprisingly common blind spot.

  8. Vector art, which Inkscape makes, scales to any size without loss of resolution. Raster art like bitmaps lose quality and become pixelated when scaled larger than their original size—the bigger the worse.

    Dropping a bitmap into Inkscape doesn't automagically turn it into vector-based art, but Inkscape does include a tracing/vectorization function that is almost magic. It works better on some raster art than others. It works pretty well for line art.

    The resolution of some raster art can be artificially enhanced by resizing with interpolation. Sometimes good, smooth-looking results can be achieved with a combination of re-sizing, increasing resolution, blurring, and sharpening.

  9. Thanks, folks. I'm not entirely unfamiliar with Inkscape, I'd even used the Trace Bitmap feature before, but for the life of me couldn't find it last night. Bless you Jensan. And thanks for the details Paul.

    So it seems like the DIY map maker that might possibly want to blow a map up into a table sized affair has 4 options:

    1) Do it by hand on a big piece of paper.
    2) Work with the raster image and hope it doesn't look too crappy when resized then blurred/sharpened.
    3) Work with a vector image, either from scratch or trace the raster image in, and hope the printer can work with svg. Also svgs tend to look more angular/cartoony to me.
    4) Do it by hand in a 300 DPI+ digital file as a raster image.

    I can't really do the back and forth option you mention Ark, I don't have a scanner.

    Zak and C'nor: Coffee. Pour just enough to barely cover the paper in a cookie sheet and as it dries it absorbs. End result, looks old as hell.

  10. I'm afraid I may have come off sounding a little too knowledgeable from my last comment. I've been playing with Inkscape for a bit now, trying to trace svgs from other maps and I don't know how you managed such a good job Jensan. There is some hoodoo involved in this.

    Learning this is going to be a long row to hoe . . .

  11. If you are going to use a paint program such as GIMP or Photoshop and you have the memory resources on your computer, make your file much bigger than you plan to print it out and always set your resolution to 300 dpi. It's much easier to go down than up. I usually set my maps up as 48" x 36" or somewhere in that neighborhood (of course, the files are freakin' HUGE). Having said that, I've been tinkering with the idea of using Illustrator for my maps as well, so that the images stay nice and clean at any size.

  12. OK, maybe you thought you were free of this...

    300dpi is magazine resolution: it's good for professional jobs, and offers a handy gold standard. Depending on the printer and paper you're using, however, you might not be able to see results better than 200dpi - with say a home inkjet printer on plain paper.

    Trying to scale up small raster images is a long road of pain. You can do it a bit if the start and desired end resolutions aren't radically different, but getting results that are ready for primetime will take about as long as redrawing the sucker (and probably will involve significant redrawing). I'd say this is the least attractive option.

    Vector images can give beautiful results that aren't cartoony at all, if you put in a lot of time. Where they tend to fall down is if you have variable line weight (thickness).

    If you're making Great Big raster files per Malakor you have to pay careful attention to the line weight you're using and how much information you're putting in an image - if you want to shrink the map down for easy transfer or the web or whatever afterwards you can end up with skinny tiny lines if you're not careful. It can be really tempting to stuff data in there and cover a big map area in high detail that won't translate to a smaller print (prime example: Nancy Chandler's heavily annotated maps of Chiang Mai and Bangkok - they're brilliant but just don't work below their broadsheet print size).

    In raster editors (photoshop) I love layers with a fierce passion. They're purpose made for editing maps. You can make one master doc with all your information on it and then just release to the players those bits you want them to have. Print on trace or acetate and they can reproduce the layers themselves and find clues (not very D&D, more Top Secret, but very satisfying).