User manual

Creating Projects

UM-2014.1-07

format maintaining the source image aspect ratio. This may result in a

cropped or blanked image, depending on the difference between the

source and output resolution and aspect ratio.

Filtering

The filter type selects the mechanism used to transform the pixels in the

source image to the new output. This mechanism involves calculating the

value of an output pixel as an aggregation of contributing source pixels. How

the various pixel contributions are weighed defines the filter.

In order of worst to best (or increasing accuracy) :

No Filtering

Only the source pixel at the center of the projected boundary is

sampled. This method is very prone to visible artefacts such as jagged

image edges.

Bilinear Filtering

The four pixels in the source image that are closest to the center of the

projected boundary are sampled. Their weighting is based on the

relative proximity to the center of the projected pixel boundary. This

produces an accurate colour result but doesn't cut down aliasing as well

as Gaussian does. Box and bilinear will produce very similar results for

small scale reductions, but due to the nature of the software coding

bilinear is generally the fastest of these two options.

Box Filtering

All pixels falling within the projected pixel boundary are sampled and

their weight is proportional to their area that lies within the projected pixel

boundary. Box and bilinear filtering will produce very similar results for

small scale reductions, but box can produce better results for larger

scale reductions.

Gaussian Filtering

All pixels falling within the projected pixel boundary are sampled and

weighted using a gaussian filter kernel. This produces better results

than the box or bilinear filters in so far as it results in less aliasing, but is

slower.

ZOM Filtering

Uses a sinc filter and is the best general filter for up and down-scaling,

providing a sharp result without artefacts. This is the default setting.

Lanczos Filtering

A windowed form of the sinc filter which may give better results in some

cases.