<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-AU" link="blue" vlink="purple" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I’ve found if you tick “Use 0 for transparency when needed” in the transformation settings, before you georeference, the bands you mention will automatically be transparent.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">This only seems to be necessary if you start with a jpeg.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">If you start with a tif or png format image, that supports transparency, the resulting image has transparent borders regardless of the setting.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">This is probably the same as Nicolas’ method, just that qgis does it for you. Nicolas’ method is more useful if you already did the georeferencing and have not saved GCPs to do it again.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">For clipping – look in the raster menu – Extraction, there are two options, clip to extent or clip to mask layer.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Another useful trick with scanned maps is, if you have scanned a line drawing type map that is predominantly white, try setting rendering mode to multiply – this makes white areas completely transparent
so allows you to overlay the scanned map over other data, photos etc. very easily.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Qgis-user <qgis-user-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Firstname Lastname<br>
<b>Sent:</b> Friday, 3 September 2021 1:39 AM<br>
<b>To:</b> qgis-user@lists.osgeo.org<br>
<b>Subject:</b> [Qgis-user] georeferencing<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">i have successfully georreferenced several maps in QGIS. The georeferencing tool leaves a black band around the rotated and shifted image. is there any way to get rid of this. also, i would like to clip some of these images to get rid
of the margin material. is there a way to do this in QGIS?<br clear="all">
-- <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal">Byron Veilleux, MSc. P.Geo<o:p></o:p></p>
<div>
<p class="MsoNormal">Conjugate Geologic Services Limited<o:p></o:p></p>
</div>
</div>
</div>
</div>
<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2">
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</div>
</body>
</html>