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<p>I use PDF as well, there you can not save a background-color or
something like that.</p>
<p>This should be better an option in QGIS to "set the colors of the
black recangles" ;-)<br>
</p>
<p>thanks all.<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">Am 01.10.2021 um 23:19 schrieb Nicolas
Cadieux:<br>
</div>
<blockquote type="cite"
cite="mid:697771e0-7f3c-13e4-f0be-b361a31a5cd6@gmail.com">
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<p>Hi,</p>
<p>It's quite simple, you just need to set the nodata value (what
you call the background-color) in the original file and then
save it. The complication is that this requires that the
datatype for the file accepts the no data value. This part is
harder to figure out for your not used to dealing with
datatypes. Perhaps, what should be asked for is a check to see
if the nodata in the translate tool check in compatibility with
the datatype format. Another possibility is to allow for setting
the nodata value (other than zero) in the Georeferencer tool
(for both the input file and the output file).<br>
</p>
<p>Nicolas<br>
</p>
<div class="moz-cite-prefix">On 2021-10-01 4:04 p.m., L.W. wrote:<br>
</div>
<blockquote type="cite"
cite="mid:31726384-91f6-049a-bf01-a99b92af3d67@gmx.de">
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charset=UTF-8">
<p>sounds like rocketscience ... for a simple task to set the
background-color ...</p>
<p>may be I am searching the web where I have to place my
feature request for this ...<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">Am 01.10.2021 um 21:39 schrieb
Nicolas Cadieux:<br>
</div>
<blockquote type="cite"
cite="mid:3dc56dfb-36d3-0f00-87a2-90ff10421f46@gmail.com">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<p>Hi,<br>
</p>
<p>Start by setting the nodata value in the input raster.
(raster/conversion/translate/Assign a specific nodata value
to output bands). Make sure you select a data type that
allows your nodata value. For example, if you select <span
style="color: rgb(0, 0, 0); font-family: Lato, 'Open
Sans', 'Lucida Grande', 'Segoe UI', Arial, sans-serif;
font-size: 14.399999618530273px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0.4);
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); display: inline !important; float: none;">Byte
- Eight bit unsigned integer, and a no data value of <b>-999</b>,
-999 does not exist in that data type so the nodata values
will be 0 therefore affecting all black pixels in the
image. Select something like int16 of float32... and a no
data value of -999 for the test. Load the new raster and
in the layer properties, make sure you have been
successful changing the nodata values.<br>
</span></p>
<p><span style="color: rgb(0, 0, 0); font-family: Lato, 'Open
Sans', 'Lucida Grande', 'Segoe UI', Arial, sans-serif;
font-size: 14.399999618530273px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0.4);
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); display: inline !important; float: none;">Then,
when georeferencing, make sure you <b>DO NOT select "Use
0 for transparency when needed".</b> The nodata from
the georefrenced file will be taken from the original file
(-999). Therefore, pixels with the value 0 in the image
will not be affected.</span></p>
<p><span style="color: rgb(0, 0, 0); font-family: Lato, 'Open
Sans', 'Lucida Grande', 'Segoe UI', Arial, sans-serif;
font-size: 14.399999618530273px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0.4);
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); display: inline !important; float: none;">Nicolas<br>
</span></p>
<p><span style="color: rgb(0, 0, 0); font-family: Lato, 'Open
Sans', 'Lucida Grande', 'Segoe UI', Arial, sans-serif;
font-size: 14.399999618530273px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0.4);
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); display: inline !important; float: none;"><br>
</span></p>
<div class="moz-cite-prefix">On 2021-10-01 2:33 p.m., L.W.
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:eb05aed0-f992-6244-eda9-3346417c8424@gmx.de">
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charset=UTF-8">
<p>Hi,</p>
<p>nope this isn't what I want ... it is the same as setting
transparent color manually.</p>
<p>I am using PDF and TIF for georeferencing.</p>
<p>Regards</p>
<p>Without no-data-0 or transparent-color:<br>
</p>
<p><img src="cid:part1.ED9FAC04.AA2D139F@gmx.de" alt=""
class=""></p>
<p>Set transparent-color to 0,0,0 or use no-data-0:<br>
</p>
<p><img src="cid:part2.C04FBB73.7C7777C7@gmx.de" alt=""
class=""></p>
<p><br>
</p>
<div class="moz-cite-prefix">Am 01.10.2021 um 19:26 schrieb
Charles Dixon-Paver:<br>
</div>
<blockquote type="cite"
cite="mid:CAK2KqicgxUWu=Vv04hmZA3JhEJWbfyyEg=8b_BoVcJt+CeA7EA@mail.gmail.com">
<meta http-equiv="content-type" content="text/html;
charset=UTF-8">
<div dir="ltr">I just loaded an unreferenced png with
black content into qgis, then set the nodata value
to 99999, then did a fake georeference with arbitrary
coordinates, and the result seemed to be rotated without
any background pixels. Using 3.20 on Windows. The
geoereferencer has a checkbox for setting nodata to 0,
so uncheck that first. Otherwise, if you're still unable
to get the "triangles" to change, my previous messages
should still apply.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, 1 Oct 2021 at
18:27, L.W. <<a href="mailto:eaglelw@gmx.de"
moz-do-not-send="true">eaglelw@gmx.de</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<p>yes, maybe to orange, a color that is not in the
original image, so I can do this color
transparent.</p>
<p><br>
</p>
<div>Am 01.10.2021 um 18:25 schrieb David Strip:<br>
</div>
<blockquote type="cite">
<div>When georeferencing, aren't the areas outside
the original image, eg, the "triangles"
resulting from rotation, treated as no data?
Wouldn't this issue be resolved by setting the
no data value to something other than black?<br>
Just guessing here, obviously.<br>
<br>
<br>
On 10/1/2021 2:36 AM, L.W. wrote:<br>
</div>
<blockquote type="cite">
<p>Thanks for answering, but I think this is not
the way I want to go ...</p>
<p>Or, I do not have written detailed.<br>
</p>
<p>I have a raster image e.g. a white rectangle,
after setting the points, QGIS rotats this
image, let's say, by 45 degrees.</p>
<p>The corners of the imported image are now
black triangles.</p>
<p>I do want to have e.g. red triangles ...</p>
<p>Regards<br>
</p>
<p><br>
</p>
<div>Am 01.10.2021 um 09:50 schrieb Charles
Dixon-Paver:<br>
</div>
<blockquote type="cite">
<div dir="ltr">There's not really any way for
a GIS system to automatically differentiate
between black background pixels and black
data pixels. QGIS supports users setting
custom pixel values to render as transparent
pixels, but it's left up to users to ensure
that their data and background values are
different.<br>
<br>
From my view, there are a couple of options
when it comes to fixing this issue in your
data. One is to use an image processing tool
like GIMP or Photoshop effectively, but that
requires retaining the geographic
information and knowing how to reprocess the
raster accordingly.<br>
<br>
The simplest solution I'm aware of is
probably to follow this workflow in QGIS:<br>
<ul>
<li>Start a new QGIS project</li>
<li>Set all black pixels to transparent in
the transparency tab of the raster layer
properties</li>
<li>Digitize a "bounding area" - you can
do this with a memory layer</li>
<li>Move your vector layer to render
underneath the raster</li>
<li>Give the vector a simple black
symbology</li>
<li>Use the "Convert map to raster" tool
from the processing toolbox</li>
</ul>
<div>There are a wide number of variations
on that workflow that are possible of
course, but I think that's the easiest to
get started.</div>
</div>
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<pre class="moz-signature" cols="72">--
Nicolas Cadieux
<a class="moz-txt-link-freetext" href="https://gitlab.com/njacadieux" moz-do-not-send="true">https://gitlab.com/njacadieux</a></pre>
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<pre class="moz-signature" cols="72">--
Nicolas Cadieux
<a class="moz-txt-link-freetext" href="https://gitlab.com/njacadieux" moz-do-not-send="true">https://gitlab.com/njacadieux</a></pre>
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