Module imagingbook.spectral

Package imagingbook.spectral.dft

Class Dft2dDirect

java.lang.Object

imagingbook.spectral.dft.Dft2dDirect

All Implemented Interfaces:

Dft2d

Direct Known Subclasses:

Dft2dDirect.Double, Dft2dDirect.Float

public abstract class Dft2dDirect
extends Object

Direct (slow) implementation of the 2-dimensional DFT using tabulated sine and cosine values. Note that this class has no public constructor - instantiate sub-class Dft2dDirect.Float or Dft2dDirect.Double instead, as shown below. See Ch. 19 of [1] for additional details.

Usage example (for float data):

 float[][] re = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {-2, -1, 0}};
 float[][] im = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}, {0, 0, 0}};
 int w = re.length;       // w = 4
 int h = re[0].length;    // h = 3
 Dft2d.Float dft = new Dft2dDirect.Float(w, h);
 dct.forward(re, im);  // re/im now is the 2D DFT spectrum
 dct.inverse(re, im);  // re/im now is the original 2D signal 
 ...

[1] W. Burger, M.J. Burge, Digital Image Processing – An Algorithmic Introduction, 3rd ed, Springer (2022).

See Also:

• Dft1dDirect

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Dft2dDirect.Double	Two-dimensional DFT implementation using double data.
static class	Dft2dDirect.Float	Two-dimensional DFT implementation using float data.

Method Summary

Modifier and Type	Method	Description
int	getHeight()	Returns the 'height' of the 2D data array (length of dimension 1).
ScalingMode	getScalingMode()	Returns the scaling mode of this DFT (see ScalingMode).
int	getWidth()	Returns the 'width' of the 2D data array (length of dimension 0).

Methods inherited from class java.lang.Object

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

Method Details

getWidth

public int getWidth()

Description copied from interface: Dft2d

Returns the 'width' of the 2D data array (length of dimension 0). Data arrays are indexed as data[x][y], with 0 ≤ x < width and 0 ≤ y < height.

Specified by:

getWidth in interface Dft2d

Returns:

the width of the 2D data array

getHeight

public int getHeight()

Description copied from interface: Dft2d

Returns the 'height' of the 2D data array (length of dimension 1). Data arrays are indexed as data[x][y], with 0 ≤ x < width and 0 ≤ y < height.

Specified by:

getHeight in interface Dft2d

Returns:

the height of the 2D data array

getScalingMode

public ScalingMode getScalingMode()

Description copied from interface: Dft2d

Returns the scaling mode of this DFT (see ScalingMode).

Specified by:

getScalingMode in interface Dft2d

Returns:

the scaling mode of this DFT.