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net.sourceforge.jiu.geometry
Class Resample

java.lang.Object
  extended bynet.sourceforge.jiu.ops.Operation
      extended bynet.sourceforge.jiu.ops.ImageToImageOperation
          extended bynet.sourceforge.jiu.geometry.Resample

public class Resample
extends ImageToImageOperation

Resizes grayscale and truecolor images using filters. For other image types (including paletted or bilevel images), you might want to use the ScaleReplication class or convert the images to grayscale (or RGB truecolor) first and then use this class. Several algorithms for resampling are implemented, they differ in resulting image quality and computational complexity.

Usage example

This will scale image to 150 percent of its original size in both directions, using the Lanczos3 filter type:
 Resample resample = new Resample();
 resample.setInputImage(image);
 resample.setSize(image.getWidth() * 3 / 2, image.getHeight() * 3 / 2);
 resample.setFilter(Resample.FILTER_TYPE_LANCZOS3);
 resample.process();
 PixelImage scaledImage = resample.getOutputImage();
 

Known problems

Origin

This code is a port of Anders Melander's Object Pascal (Delphi) unit resample.pas to Java. The Delphi code is an adaptation (with some improvements) of Dale Schumacher's fzoom C code. Check out the homepage for the Delphi resample code, a demo application to compare the different filtering algorithms is also provided: http://www.melander.dk/delphi/resampler/index.html. You will also find the original C code there.

Theory

The theoretical background for all implementations is Dale Schumacher's article General Filtered Image Rescaling in Graphics Gems III, editor David Kirk, Academic Press, pages 8-16, 1994.

The Graphics Gems Repository can be found at http://www.acm.org/tog/GraphicsGems/. It also includes information on the books and how to order them.

Author:
Marco Schmidt

Field Summary
static int FILTER_TYPE_B_SPLINE
          Constant for the B-Spline filter.
static int FILTER_TYPE_BELL
          Constant for the Bell filter.
static int FILTER_TYPE_BOX
          Constant for the Box filter (also known as Nearest Neighbor filter).
static int FILTER_TYPE_HERMITE
          Constant for the Hermite filter.
static int FILTER_TYPE_LANCZOS3
          Constant for the Lanczos3 filter.
static int FILTER_TYPE_MITCHELL
          Constant for the Mitchell filter.
static int FILTER_TYPE_TRIANGLE
          Constant for the Triangle filter (also known as Linear filter or Bilinear filter).
 
Constructor Summary
Resample()
           
 
Method Summary
 ResampleFilter getFilter()
          Returns the filter to be used in this operation.
static String[] getFilterNames()
          Returns the names of all predefined filters.
static int getNumFilters()
          Returns the number of predefined filters.
 void process()
          This method does the actual work of the operation.
 void setFilter(int filterType)
          Sets a new filter type, using the default sampling radius of that filter.
 void setFilter(int filterType, float samplingRadius)
          Sets a new filter type with a user-defined sampling radius.
 void setFilter(ResampleFilter newFilter)
          Set a new filter object to be used with this operation.
 void setSize(int width, int height)
          Set the pixel resolution of the output image.
 
Methods inherited from class net.sourceforge.jiu.ops.ImageToImageOperation
canInputAndOutputBeEqual, ensureImagesHaveSameResolution, ensureInputImageIsAvailable, ensureOutputImageResolution, getInputImage, getOutputImage, setCanInputAndOutputBeEqual, setInputImage, setOutputImage
 
Methods inherited from class net.sourceforge.jiu.ops.Operation
addProgressListener, addProgressListeners, getAbort, removeProgressListener, setAbort, setProgress, setProgress
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

FILTER_TYPE_BOX

public static final int FILTER_TYPE_BOX
Constant for the Box filter (also known as Nearest Neighbor filter).

See Also:
Constant Field Values

FILTER_TYPE_TRIANGLE

public static final int FILTER_TYPE_TRIANGLE
Constant for the Triangle filter (also known as Linear filter or Bilinear filter).

See Also:
Constant Field Values

FILTER_TYPE_HERMITE

public static final int FILTER_TYPE_HERMITE
Constant for the Hermite filter.

See Also:
Constant Field Values

FILTER_TYPE_BELL

public static final int FILTER_TYPE_BELL
Constant for the Bell filter.

See Also:
Constant Field Values

FILTER_TYPE_B_SPLINE

public static final int FILTER_TYPE_B_SPLINE
Constant for the B-Spline filter.

See Also:
Constant Field Values

FILTER_TYPE_LANCZOS3

public static final int FILTER_TYPE_LANCZOS3
Constant for the Lanczos3 filter.

See Also:
Constant Field Values

FILTER_TYPE_MITCHELL

public static final int FILTER_TYPE_MITCHELL
Constant for the Mitchell filter.

See Also:
Constant Field Values
Constructor Detail

Resample

public Resample()
Method Detail

getFilter

public ResampleFilter getFilter()
Returns the filter to be used in this operation.

Returns:
ResampleFilter object or null if none was defined yet

getFilterNames

public static String[] getFilterNames()
Returns the names of all predefined filters. Each FILTER_TYPE_xyz constant can be used as an index into the array that is returned. Names are retrieved by creating an object of each predefined filter class and calling its getName method.

Returns:
String array with filter names

getNumFilters

public static int getNumFilters()
Returns the number of predefined filters.

Returns:
number of filters

process

public void process()
             throws MissingParameterException,
                    WrongParameterException
Description copied from class: Operation
This method does the actual work of the operation. It must be called after all parameters have been given to the operation object.

Overrides:
process in class Operation
Throws:
MissingParameterException - if any mandatory parameter was not given to the operation
WrongParameterException - if at least one of the input parameters was not initialized appropriately (values out of the valid interval, etc.)

setSize

public void setSize(int width,
                    int height)
Set the pixel resolution of the output image.

Parameters:
width - the horizontal resolution of the output image
height - the vertical resolution of the output image

setFilter

public void setFilter(ResampleFilter newFilter)
Set a new filter object to be used with this operation.

Parameters:
newFilter - a resample filter to be used for scaling

setFilter

public void setFilter(int filterType)
Sets a new filter type, using the default sampling radius of that filter.

Parameters:
filterType - the new filter type, one of the FILTER_TYPE_xyz constants of this class

setFilter

public void setFilter(int filterType,
                      float samplingRadius)
Sets a new filter type with a user-defined sampling radius.

Parameters:
filterType - the new filter type, one of the FILTER_TYPE_xyz constants of this class
samplingRadius - the sampling radius to be used with that filter, must be larger than 0.0f

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Copyright © 2000, 2001, 2002, 2003, 2004 Marco Schmidt