core.image
Class Accum2Image

java.lang.Object
  core.image.ScalarImage
      core.image.AccumImage
          core.image.Accum2Image

public class Accum2Image

extends AccumImage

Stores a float image with alpha^2 = < width, height, float-buffer, alpha-buffer, minalpha, coverage >. An Accum2Image extends AccumImage so that the samples contribute in a such a way that the output variance is normalized. The float channel stores the sample sum with the alpha premultiplied, and the alpha channel stores the sum of the squares of the alpha amounts. This way, computing the final sample value is simple: sample = Sum(s[i]*sa[i])/Sqrt(Sum(sa[i]^2)) = f/Sqrt(a) If the samples accumulated have a Gaussian distribution, the final sample will have the same distribution.

Version:

1.0

Author:

Andreas Sundquist

Field Summary

Fields inherited from class core.image.AccumImage

a, coverage, minalpha

Fields inherited from class core.image.ScalarImage

f, height, offset, size, width

Constructor Summary

Accum2Image(int width, int height)
Constructs a new Accum2Image = < width, height, zero-buffer, zero-buffer, 1.0, 0 >

Method Summary

void	Accumulate(int x, int y, double s, double sa) Adds "s" and "sa"^2 to the scalar and alpha values at (x, y) if it is in-bounds.
void	Clear() Clears both the scalar and alpha components in "this"
double	get(int x, int y) Returns: the value at (x, y) with the alpha divided out.
void	Normalize() Divides out the alpha component in "this", renormalizing it to 1.0.
void	Normalize(int x, int y) Normalize the alpha value of a particular pixel, dividing out the square root of the alpha channel.
void	Set(int x, int y, double s, double sa) Sets the scalar and alpha value at (x, y) to (s, sa^2).
void	SetAlpha() Sets the scalar component of "this" to the alpha component
void	SetZero() Sets the samples in "this" to zero, with an alpha of 1.0

Methods inherited from class core.image.AccumImage

Accumulate, AccumulateBilinear, AccumulateBilinear, Copy, Copy, getAlpha, hasSingularity

Methods inherited from class core.image.ScalarImage

Add, Clamp, Convolve3x3, Copy, Copy, getBilinear, getBilinear, inBounds, inBounds, inBounds, Modulate, Power, Rescale, Set, SetRandom, SetRandom, StretchBilinear, Vec2FieldMagnitude, Vec2FieldZero

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Accum2Image

public Accum2Image(int width,
                   int height)

Constructs a new Accum2Image = < width, height, zero-buffer, zero-buffer, 1.0, 0 >

Method Detail

SetZero

public void SetZero()

Sets the samples in "this" to zero, with an alpha of 1.0

Overrides:

SetZero in class AccumImage

Clear

public void Clear()

Clears both the scalar and alpha components in "this"

Overrides:

Clear in class AccumImage

SetAlpha

public void SetAlpha()

Sets the scalar component of "this" to the alpha component

Overrides:

SetAlpha in class AccumImage

Normalize

public void Normalize()

Divides out the alpha component in "this", renormalizing it to 1.0. Since the alpha channel stores the sum of the squares of the alphas, we actually divide out the square root of the alpha value.

Overrides:

Normalize in class AccumImage

Normalize

public void Normalize(int x,
                      int y)

Normalize the alpha value of a particular pixel, dividing out the square root of the alpha channel.

Overrides:

Normalize in class AccumImage

get

public double get(int x,
                  int y)

Returns: the value at (x, y) with the alpha divided out. Requires: 0<=x

Overrides:

get in class AccumImage

Set

public void Set(int x,
                int y,
                double s,
                double sa)

Sets the scalar and alpha value at (x, y) to (s, sa^2). If (x, y) is out-of-bounds, this has no effect.

Overrides:

Set in class AccumImage

Accumulate

public void Accumulate(int x,
                       int y,
                       double s,
                       double sa)

Adds "s" and "sa"^2 to the scalar and alpha values at (x, y) if it is in-bounds.

Overrides:

Accumulate in class AccumImage