The HSVTool has three functions listed below. Though it is capable and powerful, it is possible to live without it, as most of its functionality is covered by other nodes.
Using the the 'srccolor' and 'dstcolor' parameters, a source and destination color are defined. The limits of the replacement are determined by the three groups of parameters: 'Hue', 'Saturation' and 'Brightness'. This functionality is of only occasional use.
- Hue: 'Rotation' rotates the hue values of an image. Above it are two sliding poiunts which define the range of this adjustment. 'Range Rolloff' softens its limit values and 'Saturation' defines its sits saturation limits. Maybe useful if you require hippy flashback effects.
- Saturation: operates in a similar way to 'Hue', except that it acts upon the saturation values of select colors. More refined saturation adjustments can be acquired from the HueCorrect node.
- Lightness: operates in a similar way to 'Hue', except that it acts upon the lightness values of select colors. More refined lightness adjustments can be acquired from the HueCorrect node.
The hue keyer functionality of this node is more useful, but more difficult to find. In order for this function to work the 'is' parameter of the 'output' (at the bottom of the panel) needs to be changed from the default 'hue' to 'all'. When using this node as a Keyer, it is wise to set up an extra viewer window and set it to display the alpha. To use it as a keyer first set the 'Range' parameter of the 'Hue' set and then work down the other parameters, tuning the result with the 'range Falloff' and 'Adjustment' parameters.
The only advantage that this node has over the less complex HueKeyer is that it can restrict the range to limited bands (e.g. between .2 and .7 saturation value).
Double tip: like any color node, this is best understood by trying it out on a ColorWheel.