Class TurbulencePatternRed

java.lang.Object
org.apache.batik.ext.awt.image.rendered.AbstractRed
org.apache.batik.ext.awt.image.rendered.TurbulencePatternRed
All Implemented Interfaces:
RenderedImage, CachableRed

public final class TurbulencePatternRed extends AbstractRed
This class creates a RenderedImage in conformance to the one defined for the feTurbulence filter of the SVG specification. What follows is my high-level description of how the noise is generated. This is not contained in the SVG spec, just the algorithm for doing it. This is provided in the hope that someone will figure out a clever way to accelerate parts of the function. gradient contains a long list of random unit vectors. For each point we are to generate noise for we do two things. first we use the latticeSelector to 'co-mingle' the integer portions of x and y (this allows us to have a one-dimensional array of gradients that appears 2 dimensional, by using the co-mingled index). We do this for [x,y], [x+1,y], [x,y+1], and [x+1, y+1], this gives us the four gradient vectors that surround the point (b00, b10, ...) Next we construct the four vectors from the grid points (where the gradient vectors are defined) [these are rx0, rx1, ry0, ry1]. We then take the dot product between the gradient vectors and the grid point vectors (this gives the portion of the grid point vector that projects along the gradient vector for each grid point). These four dot projects are then combined with linear interpolation. The weight factor for the linear combination is the result of applying the 's' curve function to the fractional part of x and y (rx0, ry0). The S curve function get's it's name because it looks a bit like as 'S' from 0->1.
  • Constructor Details

    • TurbulencePatternRed

      public TurbulencePatternRed(double baseFrequencyX, double baseFrequencyY, int numOctaves, int seed, boolean isFractalNoise, Rectangle2D tile, AffineTransform txf, Rectangle devRect, ColorSpace cs, boolean alpha)
      Parameters:
      baseFrequencyX - x-axis base frequency for the noise function along the x-axis
      baseFrequencyY - y-axis base frequency for the noise function along the x-axis
      numOctaves - number of octaves in the noise function. Positive integral value.
      seed - starting number for the pseudo random number generator
      isFractalNoise - defines whether the filter performs a fractal noise or a turbulence function.
      tile - defines the tile size. May be null if stitchTiles is false. Otherwise, should not be null.
      txf - The affine transform from device to user space.
      cs - The Colorspace to output.
      alpha - True if the data should have an alpha channel.
  • Method Details

    • getBaseFrequencyX

      public double getBaseFrequencyX()
    • getBaseFrequencyY

      public double getBaseFrequencyY()
    • getNumOctaves

      public int getNumOctaves()
    • getSeed

      public int getSeed()
    • getTile

      public Rectangle2D getTile()
    • isFractalNoise

      public boolean isFractalNoise()
    • getChannels

      public boolean[] getChannels()
    • setupSeed

      public final int setupSeed(int seed)
    • random

      public final int random(int seed)
    • copyData

      public WritableRaster copyData(WritableRaster dest)
      Generates a Perlin noise pattern into dest Raster.
      Parameters:
      dest - Raster to fill with the pattern.