Ert:
With a jpg or png file, the coordinate data are stored in the world file
(a simple text file with the pixel x gsd , rotation,pixel y gsd, x
coordinate, top left, y coordinate top left - see sample below). For a
pdf, the coordinate data is stored within the pdf and you would have to
check the geo-pdf specs to see where they are stored. If you write a
geotiff, the coordinates will be contained withing the file header.
Sample tiff world file (*.tfw)
0.0250000000
0.000000
0.000000
-0.0250000000
674643.3881379978
4945024.4282323727
Kirk
On 6/4/2019 1:48 PM, Alex M wrote:
Nyall,
I just did a test like Kirk png and jpg do not contain EXIF coordinates.
For the purposes of this discussion the original poster wants to know
which formats drop the location data, and it appears jpg and png are
safe for that purpose. I would advise that not every format will behave
the same, as we all seem to agree a tiff from the Image Save should have
the location in it's metadata. Though I know a good way to strip that
out - GIMP or Photoshop, open & export usually kills all metadata,
command line Photography tools might also (e.g. imagemagick).
Tested with QGIS 3.4
Thanks,
Alex
On 6/3/19 16:16, Nyall Dawson wrote:
On Tue, 4 Jun 2019 at 09:13, Fernando M. Roxo da Motta <pe...@roxo.org> wrote:
On Mon, 3 Jun 2019 11:01:06 -0300, Kirk Schmidt
<k...@nortekresources.com> wrote:
Hi Ert:
You can save locational data in jpg and pdf files from within the
Print Composer window. Under composition tab on the right hand side
of the window, scroll down and check the Save World File checkbox.
Export your map/composition as a jpg or pdf and the geolocation data
will be written to a world file for a jpg and internally for a pdf.
Just to be sure that I understood it correctly. If I save as jpg
the geolocation information will be only written to the world file if I
check the Save World File checkbox. That means that, regardless to
check or not that checkbox, the jpg image will not contain any
geolocation information.
Is that correct?
Incorrect. It will always be embedded directly inside the image
metadata where possible. The "create world file" checkbox only
controls whether an external text file with the referencing
information is also created.
Nyall
Good luck
Kirk Schmidt
On 6/2/2019 4:26 AM, Ert Four 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"
<pe...@roxo.org> wrote:
On Thu, 30 May 2019 17:09:59 +0200 (CEST), Ert Four
<4...@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
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--
---------------- Non luctari, ludare -------------------+ WYSIWYG
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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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