Module imagingbook.spectral

Package imagingbook.spectral.dct

Class Dct1dDirect

java.lang.Object

imagingbook.spectral.dct.Dct1dDirect

All Implemented Interfaces:

Dct1d

Direct Known Subclasses:

Dct1dDirect.Double, Dct1dDirect.Float

public abstract class Dct1dDirect
extends Object

Calculates the 1D DFT using tabulated cosine values for float or double data (see sub-classes Dct1dDirect.Float and Dct1dDirect.Double, respectively). This implementation is considerably faster than the naive version without cosine tables (see Dct1dSlow). Other optimizations are possible. Note that this class has no public constructor - instantiate sub-class Dct1dDirect.Float or Dct1dDirect.Double instead, as shown below. See Sec. 20.1 of [1] for additional details.

Usage example (for float data):

 float[] data = {1, 2, 3, 4, 5, 3, 0};
 Dct1d.Float dct = new Dct1dDirect.Float(data.length);
 dct.forward(data);
 dct.inverse(data);
 ...
 

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

Version:

2022/10/23

See Also:

• Dct1dSlow
• Dct1dFast

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Dct1dDirect.Double	One-dimensional DCT implementation using double data.
static class	Dct1dDirect.Float	One-dimensional DCT implementation using float data.

Method Summary

Modifier and Type	Method	Description
int	getSize()	Returns the size of this DCT (length of data vectors).

Methods inherited from class java.lang.Object

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

Method Details

getSize

public int getSize()

Description copied from interface: Dct1d

Returns the size of this DCT (length of data vectors).

Specified by:

getSize in interface Dct1d

Returns:

the size of this DCT