[Qgis-user] Is location info included in metadata when save an image file?
Ert Four
4ert at mailbox.org
Mon Jun 3 06:56:25 PDT 2019
FYI, an update on this. I asked this question to the qgis developer list and Nyall Dawson indicated most image files will have location information embedded in them, here's what he wrote:
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yes - regardless of that setting, the outputs are georeferenced and have coordinates baked in*
(* depending on format support. SVG doesn't, certain raster formats may not -- check with GDAL whether embedded georeferencing of these is possible. It is for all the common ones at least).
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Here is the complete original message:
https://lists.osgeo.org/pipermail/qgis-developer/2019-June/057521.html
> On June 2, 2019 at 9:26 AM Ert Four <4ert at mailbox.org> wrote:
>
>
> Thank you Alex and Roxo for your replies.
>
> From what I can tell the SVG and JPG files probably don't have location info in them, but it's also hard to tell what exactly the data is in some places, especially in the SVG.
>
> It looks like qgsmaprenderertask.cpp was written two years ago, which was after 2.14 came out.
>
> I will post on the developer list per Alex's suggestion. All of this is trying to prove that something doesn't exist -- which is always hard.
>
> Thanks again.
>
>
> > On June 1, 2019 at 4:41 PM "Fernando M. Roxo da Motta" <petro at roxo.org> wrote:
> >
> >
> > On Thu, 30 May 2019 17:09:59 +0200 (CEST), Ert Four <4ert at mailbox.org>
> > wrote:
> >
> >
> > > Does any coordinate or location data get embedded in the image file
> > > if I use Project > Save as Image or Composer > Export as
> > > Image/PDF/SVG?
> > >
> > > I'm using QGIS version 2.14.3 Essen, although I would like to know
> > > about more recent versions, too, for when I upgrade later.
> > >
> > > (I'm aware of the option to check "World file on" and create a
> > > separate world file. What I need is to make sure there is no
> > > identifying info whatsoever from the project file in the image file
> > > itself.)
> > >
> > > Eg, say I have a basemap like OpenStreetMap open for a country and I
> > > load points in another layer that are inside that country. Then I
> > > zoom in on a group of points from my data layer, I turn off the
> > > basemap layer, and make a map with just my data points. I want to
> > > preserve the relative spatial relationships between my points but not
> > > reveal where in the world the map came from. If I publish this image
> > > file, might the metadata reveal the location?
> > >
> > > For the work we do, it's critically important we not unknowingly
> > > publish specific locations.
> > >
> >
> > AFAIK, if you save in PNG or JPEG format no coordinate information is
> > stored in metadata of the image:
> >
> > $ exiftool Inhambu.jpg
> > ExifTool Version Number : 10.80
> > File Name : Inhambu.jpg
> > Directory : .
> > File Size : 49 kB
> > File Modification Date/Time : 2019:06:01 11:37:04-03:00
> > File Access Date/Time : 2019:06:01 11:37:04-03:00
> > File Inode Change Date/Time : 2019:06:01 11:37:24-03:00
> > File Permissions : rw-r--r--
> > File Type : JPEG
> > File Type Extension : jpg
> > MIME Type : image/jpeg
> > JFIF Version : 1.01
> > Resolution Unit : inches
> > X Resolution : 96
> > Y Resolution : 96
> > Image Width : 917
> > Image Height : 665
> > Encoding Process : Baseline DCT, Huffman coding
> > Bits Per Sample : 8
> > Color Components : 3
> > Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2)
> > Image Size : 917x665
> > Megapixels : 0.610
> >
> > $ exiftool Inhambu.png
> > ExifTool Version Number : 10.80
> > File Name : Inhambu.png
> > Directory : .
> > File Size : 47 kB
> > File Modification Date/Time : 2019:06:01 11:37:04-03:00
> > File Access Date/Time : 2019:06:01 11:37:04-03:00
> > File Inode Change Date/Time : 2019:06:01 11:37:44-03:00
> > File Permissions : rw-r--r--
> > File Type : PNG
> > File Type Extension : png
> > MIME Type : image/png
> > Image Width : 954
> > Image Height : 652
> > Bit Depth : 8
> > Color Type : RGB with Alpha
> > Compression : Deflate/Inflate
> > Filter : Adaptive
> > Interlace : Noninterlaced
> > Significant Bits : 8 8 8 8
> > Pixels Per Unit X : 3780
> > Pixels Per Unit Y : 3780
> > Pixel Units : meters
> > Image Size : 954x652
> > Megapixels : 0.622
> >
> > If you save as geotiff the positioning information should be written
> > in metadata. I don't know about the PDF format. In any case, all
> > informations, except the CRS, will be written to the world file.
> >
> > HTH
> >
> >
> > > Thank you, first time posting, very much appreciate QGIS and its
> > > community!
> >
> >
> >
> >
> >
> >
> >
> >
> > Roxo
> >
> > --
> > ---------------- Non luctari, ludare -------------------+ WYSIWYG
> > Fernando M. Roxo da Motta <petro at roxo.org> | Editor?
> > Except where explicitly stated I speak on my own behalf.| VI !!
> > PU5RXO | I see text,
> > ------------ Quis custodiet ipsos custodes?-------------+ I get text!
> >
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