Carbon paper

Post questions on how to use or achieve an effect in Inkscape.
Amadeus12
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Joined: Sat Sep 11, 2010 4:20 pm

Carbon paper

Postby Amadeus12 » Fri Aug 26, 2011 8:12 am

I make maps for wikipedia. I redraw png-maps and create svg-maps. Like this one:
http://commons.wikimedia.org/wiki/File:Byzantine_Empire.PNG

What I have tried is to import the png-file and to open a (blank) map (svg-file). How I can trace png-file onto the svg-file in more or less the same way as ppl used carbon paper to copy files.

What I am not looking for is to use the function Trace Bitmap. I know what that can do.

I want to copy/draw the borders of the empire as portrayed in the above png-file as precisely as possible in the svg-map.

Has anyone a clue how to do that? Thank you beforehand.

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brynn
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Re: Carbon paper

Postby brynn » Fri Aug 26, 2011 12:00 pm

Absolutely can be done!

You only need one file. Open a new blank Inkscape doc and import the PNG. Create a new layer (by default, it's created above the original, which is just what you want). Usually I will reduce the opacity of the layer containing the PNG, which requires the Layers dialog (from Layers menu or button on the command bar). But it's not necessary. It just depends on your preference, and how much contrast you need to see what you're doing. Then simply draw on the new layer and trace the outline that you need.

I always just follow the outline with the Pen tool, placing nodes at strategic places. This results in a path consisting of straight segments. Then afterwards, I use the Node tool to change certain nodes to smooth, where a curve is required, and adjust the handles to match the original. Depending how much detail you need, you might want to zoom in. I've found that the more I zoom in, and the more nodes I create, the more accurrate is the result.

Rather than click with the Pen tool, which creates corner or cusp nodes, some people do a click + drag, which automatically creates a smooth node. But I find it hard to control the curve with the Pen tool. And if I have to go back with the Node tool to fix it anyway, I might as well just click to create cusp nodes.

One thing always trips me up though. I often forget to make sure I'm drawing on the new layer. Well, it's not a major problem, because you just have to move the new path(s) back to the proper layer. But it can be annoying, lol. Really it's just a matter of paying attention, for me :mrgreen:

Let us know how it goes :D

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shawnhcorey
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Re: Carbon paper

Postby shawnhcorey » Fri Aug 26, 2011 12:19 pm

Last time I did something like this, I used potrace. Since I'm using Ubuntu, I can download it with the Ubuntu Software Center but you may have to get it from Sourceforge. Your source must be a bitmap (PBM, PGM, PPM, or BMP format). To get one, import your PNG to GIMP, enhance the area you want as your object, erase everything else and then save as a bitmap.

Also see:

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brynn
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Re: Carbon paper

Postby brynn » Fri Aug 26, 2011 1:43 pm

Trace Bitmap is basically potrace!

chriswww
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Re: Carbon paper

Postby chriswww » Fri Aug 26, 2011 2:59 pm

i remember seeing another trace program that wasn't potrace...which produced good results from photographs, when enough detail level is selected. that's something that potrace can't do very well (yet?). but that's an entirely aside subject.
when i traced diagrams or maps, had the png on the lower layer locked. that way you don't accidentally select and move the png or draw on that layer.
probably some of the techniques used to produce avatars would be suitable? i don't have a knack for those things yet...and things like maps (to me) have similar qualities. when i try to trace a map or a photo, often the outline has the wrong feel, and totally unlike the original bitmap.

Amadeus12
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Joined: Sat Sep 11, 2010 4:20 pm

Re: Carbon paper

Postby Amadeus12 » Fri Aug 26, 2011 4:53 pm

I wanted to trace the map not the trace bitmap-way because the old map is of bad quality. I don't want to convert the old map into svg. I wanted to make a new map with the borders as accurately drawn onto it.

This is how I have done it: I used Trace Bitmap on the old map and opened it in Inkscape. Changed the opacity somewhat and opened the new map. Tracing is not entirely possible but it turned out pretty well.
I will try it the way brynn does next time.
This is the result:
http://commons.wikimedia.org/wiki/File:RomanEmpire_117_e.svg

Thank you for answering.

Amadeus12
Posts: 66
Joined: Sat Sep 11, 2010 4:20 pm

Re: Carbon paper

Postby Amadeus12 » Fri Aug 26, 2011 11:03 pm

Tried the way brynn works and it works fine. It is necessary to work with layers.

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Bucic
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Re: Carbon paper

Postby Bucic » Sat Aug 27, 2011 9:08 pm

There's an alternative tracing tool other than potrace (built-in into Inkscape) that was able to trace just lines etc. I forgot its name though. Send me a reminder via PM and I might dig it out for you.
!!! Support wishlist: A new perspective / transformation tool http://tinyurl.com/3uacua4
* Inkscape Tutorial Basics A different approach... http://tinyurl.com/3pextp3
* What do I use Inkscape for http://tinyurl.com/3pbna6l

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brynn
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Re: Carbon paper

Postby brynn » Sun Aug 28, 2011 7:31 am

I think the other trace engine you're all trying to remember is this: http://www.roitsystems.com/cgi-bin/autotrace/tracer.pl I didn't mention it because Amadeus12 said he/she didn't want to automatically trace it. But actually it has a centerline trace option, which might suit their needs. I'm not sure, and you'll just have to experiment with it, and see what happens.

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Bucic
Posts: 128
Joined: Fri Apr 24, 2009 2:50 am
Location: Poland

Re: Carbon paper

Postby Bucic » Sun Aug 28, 2011 7:24 pm

!!! Support wishlist: A new perspective / transformation tool http://tinyurl.com/3uacua4
* Inkscape Tutorial Basics A different approach... http://tinyurl.com/3pextp3
* What do I use Inkscape for http://tinyurl.com/3pbna6l


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