vtkApplyColors

Section: Visualization Toolkit Infovis Classes

Usage

vtkApplyColors performs a coloring of the dataset using default colors, lookup tables, annotations, and/or a selection. The output is a four-component vtkUnsignedCharArray containing RGBA tuples for each element in the dataset. The first input is the dataset to be colored, which may be a vtkTable, vtkGraph subclass, or vtkDataSet subclass. The API of this algorithm refers to "points" and "cells". For vtkGraph, the "points" refer to the graph vertices and "cells" refer to graph edges. For vtkTable, "points" refer to table rows. For vtkDataSet subclasses, the meaning is obvious.

The second (optional) input is a vtkAnnotationLayers object, which stores a list of annotation layers, with each layer holding a list of vtkAnnotation objects. The annotation specifies a subset of data along with other properties, including color. For annotations with color properties, this algorithm will use the color to color elements, using a "top one wins" strategy.

The third (optional) input is a vtkSelection object, meant for specifying the current selection. You can control the color of the selection.

The algorithm takes two input arrays, specified with SetInputArrayToProcess(0, 0, 0, vtkDataObject::FIELD_ASSOCIATION_POINTS, name) and SetInputArrayToProcess(1, 0, 0, vtkDataObject::FIELD_ASSOCIATION_CELLS, name). These set the point and cell data arrays to use to color the data with the associated lookup table. For vtkGraph, vtkTable inputs, you would use FIELD_ASSOCIATION_VERTICES, FIELD_ASSOCIATION_EDGES, or FIELD_ASSOCIATION_ROWS as appropriate.

To use the color array generated here, you should do the following:

mapper->SetScalarModeToUseCellFieldData(); mapper->SelectColorArray("vtkApplyColors color"); mapper->SetScalarVisibility(true);

Colors are assigned with the following priorities: <ol> <li> If an item is part of the selection, it is colored with that color. <li> Otherwise, if the item is part of an annotation, it is colored with the color of the final (top) annotation in the set of layers. <li> Otherwise, if the lookup table is used, it is colored using the lookup table color for the data value of the element. <li> Otherwise it will be colored with the default color. </ol>

Note: The opacity of an unselected item is defined by the multiplication of default opacity, lookup table opacity, and annotation opacity, where opacity is taken as a number from 0 to 1. So items will never be more opaque than any of these three opacities. Selected items are always given the selection opacity directly.

To create an instance of class vtkApplyColors, simply invoke its constructor as follows

  obj = vtkApplyColors

Methods

The class vtkApplyColors has several methods that can be used. They are listed below. Note that the documentation is translated automatically from the VTK sources, and may not be completely intelligible. When in doubt, consult the VTK website. In the methods listed below, obj is an instance of the vtkApplyColors class.