Saving a part of an image as a separate image

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Paul B.
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Joined: Sun Oct 07, 2018 6:42 pm

Saving a part of an image as a separate image

Postby Paul B. » Sun Oct 07, 2018 7:33 pm

Hello all,

I am working on a map of Europe and have come upon a problem that I don't know how to solve.

For this map I have downloaded fourteen scanned maps from the Perry Castaneda Library that fit my purpose almost exactly.
However, I need to combine the fourteen separate images into one. In order to do that I have created a graticule (the grid that represents meridians and parallels) that is large enough to fit all the maps into.
The maps need to be slightly "stretched" in order to fit the graticule, the paper maps weren't completely straight and flattened when they were scanned which means that they don't fit exactly into the mathematical preciseness of the graticule.

I have used Inkscape to create the graticule and edit the map scans (clipping them so that the white borders around them, with the map legend and other information, are removed and rotating them to the correct orïentation).
Later on I will also use Inkscape to trace the maps in the exact detail and colours that I want.

But first I need to "stretch" them and I have found that the best tool to do this is Adobe Illustrators Puppet Warp.
I want to do each map separately (just to keep it all neat and orderly) but now I find that when I clip a part of the graticule, save that as a separate svg-file corresponding to one of the scanned maps and then open that in Illustrator the whole unclipped thing is there. The same goes for the maps as a little fidgeting with the selection tool made clear. Though the edges that I clipped off aren't shown it is impossible to cut and paste the visible images into one because "the requested transformation would make some objects fall completely off the drawing area".

So, finally :mrgreen: , here's the question: what do I need to do in Inkscape to make sure that I only save the clipped parts of an image? How do I prevent the data of the unwanted part to still be in the new svg-file?

I'd rather solve this in Inkscape since it is my preferred drawing program. I'd like to prevent having to solve this in the overcomplicated Illustrator.

Thank you in advance for your time and effort!

Best regards,

Paul

tylerdurden
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Location: Michigan, USA

Re: Saving a part of an image as a separate image

Postby tylerdurden » Mon Oct 08, 2018 4:55 am

Seems like a lot of steps. I might use the big drawing, link to the bitmaps and use gimp's "cage transform" to stretch it while the Inkscape window is still open (overwrite the original bitmap)... Inkscape will show the updates. The bitmap can be clipped to hide unwanted areas.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

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druban
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Re: Saving a part of an image as a separate image

Postby druban » Mon Oct 08, 2018 11:07 am

"what do I need to do in Inkscape to make sure that I only save the clipped parts of an image? "

Select your clipped image, then Export png image, selection, and choose resolution and size of image in the dialog, or make bitmap copy, and set the resolution in preferences. if the result is not sharp there is some recourse, but best to export large to avoid this
Your mind is what you think it is.

Moini
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Re: Saving a part of an image as a separate image

Postby Moini » Tue Oct 09, 2018 6:13 am

Use boolean operations to cut off those parts you don't want saved in the SVG. See https://vektorrascheln.de/posts/2015/De ... operations for example.
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brynn
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Re: Saving a part of an image as a separate image

Postby brynn » Tue Oct 09, 2018 11:11 am

Or possibly crop them in a raster program before importing into Inkscape?

Depending on the complexity of the contents of the maps, I might consider tracing them first (vectorizing) and then warp the vector paths to fit the grid. Envelope deform LPE would be a good tool for the "warping". It's not automatic though, it would be tweak, tweak, tweak, to get it right. This probably would not work...or rather would be hard to do, if the maps are very complex.


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