[Qgis-user] Converting gif/jpeg images to shape files

[Andreas Neumann]

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Hi,

What is the purpose of converting these maps to vector files?
 I doubt that it makes a lot of sense to convert scanned historic maps
to a vector format (unless it is clearly a clean black and white line
graphic).

You will get all sorts of ugly artefacts and the filesize would probably
be bigger than the original rasters. Also, you would get vectors without
attribute data (except maybe color/gray values), which is also not ideal.

Probably you just want to geo-reference those scanned maps and use them
as background layers?

Andreas

On 06/27/2011 08:31 PM, Alex Mandel wrote:
> On 06/27/2011 08:36 AM, Mick wrote:
>> I have a collection of .gif and .jpg images of early maps I wish to
>> convert into ESRI shape files for integration into a set of layers of
>> 17th to 19th century Devon.
>>
>> I did stumble on to what appeared to be the tool to do it but I can't
>> find it again and can't think of the correct terminology for the
>> process so I could google with some chance of success.
>>
>> Can some kind soul please point me in the right direction.
>>
>> mick
> 
> What you want is Raster->Vector conversion. GDALtools has some stuff for
> this (or GDAL commandline), there may also be a few other plugins to try
> in the list, but if none of those work GRASS has a lot of support for
> this type of operation.
> 
> Of course that's assuming you want it automated. Depending on the
> complexity of the map you could always do it by hand.
> 
> 1st step if you can though is to Georeference the images.
> 
> Enjoy,
> Alex
> 
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