vtkImageToPolyDataFilter

Section: Visualization Toolkit Hybrid Classes

Usage

vtkImageToPolyDataFilter converts raster data (i.e., an image) into polygonal data (i.e., quads or n-sided polygons), with each polygon assigned a constant color. This is useful for writers that generate vector formats (i.e., CGM or PostScript). To use this filter, you specify how to quantize the color (or whether to use an image with a lookup table), and what style the output should be. The output is always polygons, but the choice is n x m quads (where n and m define the input image dimensions) "Pixelize" option; arbitrary polygons "Polygonalize" option; or variable number of quads of constant color generated along scan lines "RunLength" option.

The algorithm quantizes color in order to create coherent regions that the polygons can represent with good compression. By default, the input image is quantized to 256 colors using a 3-3-2 bits for red-green-blue. However, you can also supply a single component image and a lookup table, with the single component assumed to be an index into the table. (Note: a quantized image can be generated with the filter vtkImageQuantizeRGBToIndex.) The number of colors on output is equal to the number of colors in the input lookup table (or 256 if the built in linear ramp is used).

The output of the filter is polygons with a single color per polygon cell. If the output style is set to "Polygonalize", the polygons may have an large number of points (bounded by something like 2*(n+m)); and the polygon may not be convex which may cause rendering problems on some systems (use vtkTriangleFilter). Otherwise, each polygon will have four vertices. The output also contains scalar data defining RGB color in unsigned char form.

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

  obj = vtkImageToPolyDataFilter

Methods

The class vtkImageToPolyDataFilter 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 vtkImageToPolyDataFilter class.