Scaling Filters; Lanczos Filter; B-Spline Filter; C-Spline Filter - Digital Projection FUSION User Manual

6.3 Scaling filters

6.3.1 Lanczos filter

6.3.2 B-spline filter

6.3.3 C-spline filter

6.3.4 Linear interpolation filter

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Regardless of the warping algorithms selected, a scaling filter will be applied. Scaling filters
are configured using the Algorithm Setup window. Select the tab "Filter", Figure 6-2, and
select your desired filter. Four different scaling filters are supported:
• Lanczos, B-spline, C-spline, Linear
Figure 6-2. Scaling filters
The Lanczos filter is using a 4x4 kernel. This filter is recommended for use with images that
contains large amounts of fine detail, for example text with small fonts. On thin, diagonal or
curved lines, some ripple may be encountered.
The B-spline filter available in the FUSION processing system is of the type Cubic B-spline.
This filter is slightly softer than the Lanczos filter, but has better quality on curved and straight
lines. In many cases, this filer will give the best image quality and is therefore the default
selection.
The C-spline filter is short for Cubic Hermite spline interpolation. It is a filter of third-degree
spline with each polynomial of the spline in Hermite form (Named in the honour of Charles
Hermite). This filter gives a good combination of smoothness, detail and average ripple on
lines.
This filter is also a polynomial filter, but is based on linear interpolation for curve fitting.
In modern systems, it will give an unnecessarily low quality image scaling, but some
applications may still require the use of this filter.