User Guide

CHAPTER 13. FILTERS 165
13.150 Threshold Alpha
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13.151 TIFF
Overview
Allows you to configure settings for saving a TIFF (Tagged Image File Format) im-
age. TIFF files can be compressed in a number of ways to reduce the file size. LZW
(Lempel Ziv Welch) compression is the same method used in GIF images, and pro-
duces a significant reduction in file size without losing any image information (it is a
lossless method). It should be noted that LZW compression is covered by a restrictive
Unisys license.
PackBits compression is often used on Macintosh systems and is a form of Run
Length Encoding ( RLE) which, like LZW, is a lossless method.
Deflate compression, sometime known as "zip" compression, uses another variant
of the LZW compression method and so gives similar results, but is not restricted by
any licenses. LZW compression should be used on logo-type images such as maps
and line diagrams. JPEG compression is the same compression methods used when
saving JPEG files. JPEG compression should be used on photographs or realistic
scenes.
Finally, you can leave the TIFF uncompressed for maximum quality, but be warned
that file sizes can be very large.
As with JPEG (and some other formats) a comment can be added to the image up
to 32KB. A default comment for new images can be set in Preferences.
13.152 Tile
Overview
“Tile” creates multiple copies of the current image in a tiled pattern. The size of
the tiled image should be set as a multiple of the current image to get a cleanly tiled
image. For example, setting 400 x 400 for a 100 x 100 image would make the new
image contain 4 copies of the current image.
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It is often useful to select Create New Image so that the current image
remains unaltered.
13.153 Tileable Blur
Overview