Parent Topic: <A href="http://www.pcigeomatics.com/cgi-bin/pcihlp/STG|DETAILS">DETAILS</a><hr>
<H4>RESAMPLING</H4>
Resampling is the process of sampling one or more input pixels to
create one output pixel. (This is different from the transfer phase,
which merely determines where the output pixel lies on the input
image). In general, resampling is accomplished by taking a weighted
average of a small window of input pixels around some point
determined by the transform phase. The quality of the corrected
output image and the time required in calculation are highly
dependent on the resampling method chosen. STG offers three of the
more popular resampling methods: Nearest Neighbour, Bilinear
Interpolation, and Cubic Convolution.<p>
NEAREST NEIGHBOUR: This method takes the single input pixel nearest
to the transformed point as the resampled output pixel. The
advantages of this method include a very low computational cost, and
the non-alteration of input pixel grey levels. This non-alteration
is important if you are registering theme or classified data. The
disadvantage is that the output image may be jagged and blocky in
appearance if there is much rotation or scaling.<p>
BILINEAR INTERPOLATION: This method takes a weighted average of the
four input pixels around the transformed point. The advantages of
this method include low computational cost and relatively smooth
output images. The disadvantage is that the output image may appear
slightly blurred.<p>
CUBIC CONVOLUTION: STG uses the 4-point classic method. This
variation of cubic convolution uses a 4-by-4 window of input pixels.
This method is closer to the perfect sin(x)/x resampler than the
Nearest Neighbour or the Bilinear Interpolation method. The
advantage is a smooth, sharp output image. The disadvantage is a
very high computational cost.
<P>
<hr>
Parent Topic: <A href="http://www.pcigeomatics.com/cgi-bin/pcihlp/STG|DETAILS">DETAILS</a><br>
<a href="http://www.pcigeomatics.com/dev_corner/pcihlp_gateway.html">About PCI Help Gateway</a>