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:
http://www.mathplanet.com/education/geometry/transformations/transformation-using-matrices
Jan
That won't work, since it will move the corner point half a cell, and
then rotate around the new corner.
- Øyvind
On Mon, Aug 26, 2013 at 7:02 PM, Norman Vine <[email protected]
<mailto:[email protected]>> wrote:
On Aug 26, 2013, at 12:50 PM, Oyvind Idland
<[email protected] <mailto:[email protected]>> wrote:
I am currently working on a driver for a proprietary format,
which is being consumed by ArcGis via GDAL.
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:
poDS->dGeoTransform[0] = originX;
poDS->dGeoTransform[1] = cos(rotation) * cellSizeX;
poDS->dGeoTransform[2] = -sin(rotation) * cellSizeX;
poDS->dGeoTransform[3] = originY;
poDS->dGeoTransform[4] = sin(rotation) * cellSizeY;
poDS->dGeoTransform[5] = cos(rotation) * cellSizeY;
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.
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:
The cyan dot shows the pivot point:
http://i.stack.imgur.com/7HEvc.png
Is there any way to express this translation using the
geotransform matrix ?
I think this should work
poDS->dGeoTransform[0] = originX + cellSizeX/2.0;
poDS->dGeoTransform[1] = cos(rotation) * cellSizeX;
poDS->dGeoTransform[2] = -sin(rotation) * cellSizeX;
poDS->dGeoTransform[3] = originY - cellSizeY/2.0;
poDS->dGeoTransform[4] = sin(rotation) * cellSizeY;
poDS->dGeoTransform[5] = cos(rotation) * cellSizeY;
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