User Guide

GNU Image Manipulation Program
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Sample Merge
Sample Merged is an option you can set when you use the Bucket Fill tool, the Color Picker tool and various selection
tools. It is useful when you are working on an image with several layers and the active layer is either semi-transparent or
has a Layer Mode which is not set to Normal. When you check the Sample Merged option, the color which is used for the
operation is the composite color of all the visible layers. When the Sample Merged option is not checked, the color used is
the color of the active layer itself.
Saturation
This term refers to color purity. Imagine you add pigment to white paint. Saturation varies from 0 (white, fully toned
down, fully diluted) to 100 (pure color).
Supersampling
Supersampling is a more sophisticated antialiasing technique, that is, a method of reducing jagged and stair-stepped edges
along a slanted or curved line. Samples are taken at several locations within each pixel, not just at the center, and an
average color is calculated. This is done by rendering the image at a much higher resolution than the one being displayed
and then shrinking it to the desired size, using the extra pixels for calculation. The result is a smoother transition from one
line of pixels to another along the edges of objects.
The quality of the result depends on the number of samples. Supersampling is often performed at a range of 2× to 16×
the original size. It greatly increases the amount of time needed to draw the image and also the amount of space needed to
store the image in memory.
One way to reduce the space and time requirement is to use Adaptive Supersampling. This method takes advantage of the
fact that very few pixels are actually on an object boundary, so only those pixels need to be supersampled. At first, only a
few samples are taken within a pixel. If the colors are very similar to each other, only those samples are used to calculate
the final color. If not, more samples are used. This means that the higher number of samples is calculated only where
necessary, which improves performance.
SVG
SVG stands for Scalable Vector Graphics. It a format for two-dimensional vector graphics, both static and animated. You
can export GIMP paths to SVG and you can import SVG documents into GIMP from a vector graphic software. See
[WKPD-SVG] for more details.
T
TGA
TGA (TARGA Image File) is a file format which supports 8, 16, 24 or 32 bits per pixel and optional RLE compression. It
was originally developed by the Truevision company. ‘TGA’ stands for Truevision Graphics Adapter and ‘TARGA’ stands
for Truevision Advanced Raster Graphics Adapter.
TIFF
TIFF (Tagged Image File Format) is a file format which was developed primarily for scanned raster graphics for color
separation. Six different encoding routines are supported, each with one of three different image modes: black and white,
grayscale and color. Uncompressed TIFF images may be 1, 4, 8 or 24 bits per pixel. TIFF images compressed using the
LZW algorithm may be 6, 8 or 24 bits per pixel. Besides Postscript format, TIFF is one of the most important formats
for preliminary stages of printing. It is a high quality file format, which is perfect for images you want to import to other
programs like FrameMaker or CorelDRAW.
Tile
A Tile is a part of an image which GIMP currently has open. In order to avoid having to store an entire image in memory
at the same time, GIMP divides it into smaller pieces. A tile is usually a square of 64 x 64 pixels, although tiles at the
edges of an image may be smaller than that.
At any time, a tile may be in main memory, in the tile cache in RAM, or on disk. Tiles which are currently being worked
on are in main memory. Tiles which have been used recently are in RAM. When the tile cache in RAM is full, tiles which
have been used least recently are written to disk. GIMP can retrieve the tiles from RAM or disk when they are needed.
Do not confuse these tiles with those in the Tile Filter