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<font face="Times New Roman, Times, serif">The only way would be
then to concatenate the transformations: first rotate and then
translate half a pixel width. The computation can be simplified by
matrix multiplication:<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.mathplanet.com/education/geometry/transformations/transformation-using-matrices">http://www.mathplanet.com/education/geometry/transformations/transformation-using-matrices</a><br>
<br>
Jan<br>
</font>
<blockquote
cite="mid:CAEVk4t0fze0NvqTBELJEZuC6+ixMJ8xX+irb_ZT=bZijBdp_Dg@mail.gmail.com"
type="cite">
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<div dir="ltr">That won't work, since it will move the corner
point half a cell, and then rotate around the new corner.
<div><br>
</div>
<div>- Øyvind</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Mon, Aug 26, 2013 at 7:02 PM, Norman
Vine <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:nhv@cape.com" target="_blank">nhv@cape.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word"><br>
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<div>
<div class="h5">
<div>On Aug 26, 2013, at 12:50 PM, Oyvind Idland
<<a moz-do-not-send="true"
href="mailto:oyvind.idland@gmail.com"
target="_blank">oyvind.idland@gmail.com</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>
<div>I am currently working on a driver for
a proprietary format, which is being
consumed by ArcGis via GDAL.<br>
<br>
</div>
These grids sometimes has a rotation with a
specified pivot point. I managed to get
ArcGis to display the rotated grid by doing
the following: <br>
<br>
poDS->dGeoTransform[0] = originX;<br>
poDS->dGeoTransform[1] = cos(rotation) *
cellSizeX;<br>
poDS->dGeoTransform[2] = -sin(rotation) *
cellSizeX;<br>
poDS->dGeoTransform[3] = originY;<br>
poDS->dGeoTransform[4] = sin(rotation) *
cellSizeY;<br>
poDS->dGeoTransform[5] = cos(rotation) *
cellSizeY;<br>
<br>
</div>
Rotation is in radians. It works, but there is
one problem: I need to rotate the grid around
the center of the corner cell (originX,
originY), but ends up getting rotation around
the corner of the cell/raster instead.<br>
<br>
</div>
<div>There is a screenshot here, showing only
the corner pixel. The topmost grid/pixel was
translated using custom geotransform in
ArcGis, the bottom one is the result of my
GDAL rotation:<br>
The cyan dot shows the pivot point:<br>
<br>
<a moz-do-not-send="true"
href="http://i.stack.imgur.com/7HEvc.png"
target="_blank">http://i.stack.imgur.com/7HEvc.png</a><br>
</div>
<div><br>
<br>
</div>
Is there any way to express this translation
using the geotransform matrix ?<br>
</div>
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<div>I think this should work</div>
<div>
<div><br>
</div>
<div>poDS->dGeoTransform[0] = originX +
cellSizeX/2.0;</div>
<div class="im">
<div>poDS->dGeoTransform[1] = cos(rotation) *
cellSizeX;</div>
<div>poDS->dGeoTransform[2] = -sin(rotation) *
cellSizeX;</div>
</div>
<div>poDS->dGeoTransform[3] = originY -
cellSizeY/2.0;</div>
<div class="im">
<div>poDS->dGeoTransform[4] = sin(rotation) *
cellSizeY;</div>
<div>
poDS->dGeoTransform[5] = cos(rotation) *
cellSizeY;</div>
<div><br>
</div>
<div><br>
</div>
</div>
</div>
</div>
</div>
<br>
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</blockquote>
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<br>
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<br>
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