HVS ColorGIF 2.0 User Manual

Thresholding

The Thresholding parameters can be used to set a range of colors (everything darker or lighter than the target color) to a single color. This leaves more room in the palette for more visible colors, and also markedly improves compression by filtering out subtle color variations that are difficult to encode. Thresholding colors can be chosen via the preview by clicking on one of the four color swatches in the thresholding area, then clicking or dragging on the preview. The brightness (Luma) of the colors can be set with the up/down arrows. The Set To swatches allow you to determine the actual target colors by dragging the mouse in the Preview window. Note that using colored Set To settings may throw off some color calculations, so you should use care when forcing thresholded regions to a color as opposed to a shade of gray. If you observe dark or light areas changing to an odd color, make sure it isn't due to a Set To color.

To reset the thresholding colors to their default settings, click on the corresponding Off button. When the thresholding parameters are at their default settings, thresholding is effectively off. Thresholding capabilities are only available in conjunction with an Adaptive palette selection.