[Qgis-user] Is location info included in metadata when save an image file?

[Fernando M. Roxo da Motta]

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

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