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/*
* Shear
*
* Copyright (c) 2001, 2002, 2003, 2004, 2005 Marco Schmidt
* All rights reserved.
*/
package net.sourceforge.jiu.geometry;
import net.sourceforge.jiu.data.PixelImage;
import net.sourceforge.jiu.data.IntegerImage;
import net.sourceforge.jiu.ops.ImageToImageOperation;
import net.sourceforge.jiu.ops.MissingParameterException;
import net.sourceforge.jiu.ops.WrongParameterException;
/**
* Shears an image by a given angle.
* The angle must be larger than -90 and smaller than 90 degrees.
* Shearing works with all image types that implement {@link net.sourceforge.jiu.data.IntegerImage}.
* <h3>Usage example</h3>
* <pre>
* Shear shear = new Shear();
* shear.setInputImage(image); // some IntegerImage
* shear.setAngle(5.0);
* shear.process();
* PixelImage shearedImage = shear.getOutputImage();
* </pre>
* <p>
* This is an adjusted version of Jef Poskanzer's shearing code from his ACME
* package; see the
* <a target="_top" href="http://www.acme.com/java/software/Acme.JPM.Filters.Shear.html">API
* documentation page</a> of ACME's Shear class.
*
* @author Jef Poskanzer
* @author Marco Schmidt
*/
public class Shear extends ImageToImageOperation
{
private double angle;
/**
* For a given image width and shearing angle this method
* computes the width of the resulting image.
* This method is static so that it can be called easily from a GUI dialog
* or other objects that want to present the width of a sheared image.
* @param oldImageWidth horizontal resolution of the image to be sheared
* @param height height of the image to be sheared
* @param angle the angle to be used in the shearing operation
* @return width of the sheared image
*/
public static int computeNewImageWidth(int oldImageWidth, int height, double angle)
{
double shearfac = Math.tan(angle * Math.PI / 180.0);
if (shearfac < 0.0)
{
shearfac = -shearfac;
}
return (int)(height * shearfac + oldImageWidth + 0.999999);
}
/**
* Returns the angle associated with this shearing operation object.
* @return shearing angle, between -90 and 90
* @see #setAngle
*/
public double getAngle()
{
return angle;
}
private void process(IntegerImage in, IntegerImage out)
{
final int WIDTH = in.getWidth();
final int HEIGHT = in.getHeight();
int totalItems = in.getNumChannels() * HEIGHT;
int processedItems = 0;
double angle = getAngle() * Math.PI / 180.0;
double shearfac = Math.tan(angle);
if (shearfac < 0.0)
{
shearfac = -shearfac;
}
int NEW_WIDTH = (int)(HEIGHT * shearfac + WIDTH + 0.999999);
if (out == null)
{
out = (IntegerImage)in.createCompatibleImage(NEW_WIDTH, HEIGHT);
setOutputImage(out);
}
for (int c = 0; c < in.getNumChannels(); c++)
{
for (int y = 0; y < HEIGHT; y++)
{
double new0;
if (angle > 0.0)
{
new0 = y * shearfac;
}
else
{
new0 = (HEIGHT - y) * shearfac;
}
int intnew0 = (int)new0;
double fracnew0 = new0 - intnew0;
double omfracnew0 = 1.0 - fracnew0;
int prev = 0;
for (int x = 0; x < WIDTH; x++)
{
int value = in.getSample(c, x, y);
out.putSample(c, intnew0 + x, y, (int)(fracnew0 * prev + omfracnew0 * value));
prev = value;
}
out.putSample(c, intnew0 + WIDTH, y, (int)(fracnew0 * prev));
setProgress(processedItems++, totalItems);
}
}
}
public void process() throws
MissingParameterException,
WrongParameterException
{
ensureInputImageIsAvailable();
PixelImage in = getInputImage();
ensureOutputImageResolution(computeNewImageWidth(in.getWidth(), in.getHeight(), getAngle()), in.getHeight());
if (in instanceof IntegerImage)
{
process((IntegerImage)in, (IntegerImage)getOutputImage());
}
else
{
throw new WrongParameterException("Input image must implement IntegerImage.");
}
}
/**
* Sets the angle to be used in the shearing operation to the argument value.
* The angle must be larger than -90.0 and smaller than 90.0.
* @param newAngle the angle to be used in this operation
* @throws IllegalArgumentException if the argument is not in the above mentioned interval
* @see #getAngle
*/
public void setAngle(double newAngle)
{
if (newAngle <= -90.0 || newAngle >= 90.0)
{
throw new IllegalArgumentException("Angle must be > -90 and < 90; got " + newAngle);
}
else
{
angle = newAngle;
}
}
}
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