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Thread: GIMP How? The S. John Ross Woodcut technique

  1. #1

    Post GIMP How? The S. John Ross Woodcut technique

    I'm an amateur user of the GIMP, trying to recreate the excellent woodcut-seascape pattern that S. John Ross created for his Uresia maps. Mr. Ross was kind enough to post a tutorial on his website explaining how to do it in photoshop, but there are some steps I'm having trouble translating into GIMP.

    Specifically, I don't know how to create the fade-to-grey outline that the process begins with in the (as seen in the sample "simplemap" in that tutorial). And I'm completely lost in Step 7, where the grey outline is replaced by the tile pattern. The "bitmap" part is the key, since I don't see how to recreate that in GIMP. Pointers would be appreciated.
    Last edited by E.T.Smith; 08-05-2009 at 03:22 PM.

  2. #2
    Community Leader Korash's Avatar
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    I can't help you with your specific request, but a can make a suggestion.

    If you scroll down on the main page you will find a forum called Tutorials/How To... and in here you will find all sorts of tutorials of many aspects of mapping. Most of these tutorials are for either Gimp or Photoshop, and many people have posted ways of doing something close to what is shown in the tut for the other prog.

    I would suggest that you check out that Forum, as well as the WIP (Work In progress) Forum to see if any of those have your answer. You might even find other info/tricks that you might like to try out . You might get lucky and someone might actually have tried to do exacty what you are doing.

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    Professional Artist Facebook Connected Coyotemax's Avatar
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    I'm not so familiar with Gimp, but what he's doing is starting off as a greyscale file, and the "bitmap" occurs in the conversion menu (from greyscale to colour). In photoshop, typically I'm converting to RGB colour, but there are other options available. maybe that will help you track it down..

    My finished maps
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    Guild Journeyer msa's Avatar
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    I've tried to find the tools that make that process work in GIMP, but I haven't. That doesn't mean its not there... just that I wasn't smart enough to find it. You can accomplish something similar through this process:

    1. Fill the background with the woodcut water pattern
    2. Select the body of water
    3. Shrink it by X pixels and feather it 2X pixels (or less than 2X to taste)
    4. Fill the feathered selection with white (make sure the 'fill entire selection' box is checked)
    5. Gaussian blur by 5 or so pixels
    6. Use the threshold or curves menus to turn the blurry lines into tapered ones

    Its not as pretty, and takes a lot of fidgeting. There may also be a better way. Hopefully RobA will drop by and enlighten all of us, so keep up with this thread!
    Last edited by msa; 08-05-2009 at 01:50 PM.

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    Administrator RobA's Avatar
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    Post Gimp Script: Greyscale Dither

    Or a nicer dither can be obtained by using the attached gimp script (greyscale dither) that I wrote, along with a suitable woodcut dither pattern. I've attached two as samples. There are many more dither patterns here where I found the technique.

    The scriptshows up in the menus as Filters->Distorts->Greyscale Dither.

    It only works on RGB images. The cleanest results can be obtained by first scaling up the B&W layer to be dithered, then scaling it back down again. (It is optimized to produce a pure B&W image in the default mode. The greyscale modes are a bit of an experiment and aren't true to the dithering technique).

    Lastly, I attached the result of running this script on the provided S. John Ross sample, scaling it up 200%, using the woodcut 100 as a dither pattern, then scaling it back down by 50%.

    -Rob A>
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Attached Images Attached Images  
    Attached Files Attached Files

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    Guild Journeyer msa's Avatar
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    Three cheers for RobA!

    Hip hip, horray!
    Hip hip, horray!
    Hip hip, horray!

  8. #8

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    Thank you, that's all very helpful. I still can't figure out haw to get that initial fade-to-white coastline, however.

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    Administrator RobA's Avatar
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    Oh Ha!

    Simple. This is the way I do it.

    Start with black land on white sea:
    Click image for larger version. 

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    Duplicate this, and select by colour the black, then grow the selection by 1/2 the amount you want your fade to be (I used 30 pixels here), then fill with black.
    Click image for larger version. 

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    Go back to the original layer and select by colour the black again. Then invert the selection. Now Gaussian blur twice the pixel size you grew the selection:
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    Invert the selection again and fill with white Though this is purely optional if you are most likely to have a land layer above:
    Click image for larger version. 

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    Now select None, and use levels and adjust the gamma (middle slider) or use curves and drag it up an down until you get the fade out you want:
    Click image for larger version. 

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    That's it!

    -Rob A>

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