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/*
* ArrayScaling
*
* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Marco Schmidt
* All rights reserved.
*/
package net.sourceforge.jiu.util;
import java.lang.IllegalArgumentException;
/**
* This class currently only scales up an image given as a one-dimensional array
* of values.
* <p>
* <em>Note: This class should be adjusted if Java ever supports genericity.
* It could then work on all kinds of arrays.</em>
*
* @author Marco Schmidt
*/
public class ArrayScaling
{
private ArrayScaling()
{
}
/**
* Scales up the argument image by factor 2 in both directions.
* It is assumed that the first <code>width</code> times
* <code>height</code> values of <code>data</code> contain an image
* (or image channel).
* The pixels (or samples) are assumed to be laid out rows top-to-bottom,
* within each row left-to-right.
* It is further assumed that the length of the <code>data</code> array is
* at least 4 times <code>width</code> times <code>height</code>.
* This method scales up the image in <code>data</code> so that after the call to this
* method <code>data</code> can be treated as an image (a channel) that has a horizontal
* resolution of <code>width * 2</code> and a vertical resolution of
* <code>height * 2</code>.
*
* @param data the array of pixels that form the image to be flipped
* @param width the horizontal resolution of the image; must be larger than 0
* @param height the vertical resolution of the image; must be larger than 0
* @exception IllegalArgumentException if the arguments are invalid
*/
public static final void scaleUp200Percent(byte[] data, int width, int height)
throws IllegalArgumentException
{
if (data == null)
{
throw new IllegalArgumentException("Error -- data must be non-null.");
}
if (width < 1 || height < 1)
{
throw new IllegalArgumentException("Error -- both width and " +
"height must be larger than zero (width=" + width +
", height=" + height + ").");
}
if (width * height * 4 > data.length)
{
throw new IllegalArgumentException("Error -- data array must hold " +
"at least width times height times 4 values.");
}
int newWidth = width * 2;
int newHeight = height * 2;
// (1) scale up each row in horizontal direction and copy it to its destination
// at the same time
int y1 = height - 1;
int y2 = newHeight - 1;
while (y1 >= 0)
{
int x = width - 1;
int offset1 = (y1 + 1) * width - 1;
int offset2 = (y2 + 1) * newWidth - 1;
while (x > 0)
{
int v1 = data[offset1--] & 0xff;
int v2 = data[offset1] & 0xff;
data[offset2--] = (byte)v1;
data[offset2--] = (byte)((v1 + v2) >> 1);
x--;
}
byte v = data[offset1];
data[offset2--] = v;
data[offset2] = v;
y1--;
y2 -= 2;
}
// (2) take two already-copied rows from scaled image and
// interpolate the row between them
int y = newHeight - 1;
while (y > 1)
{
int offset1 = (y - 2) * newWidth;
int offset2 = offset1 + newWidth;
int offset3 = offset2 + newWidth;
for (int x = 0; x < newWidth; x++)
{
int v1 = data[offset1++] & 0xff;
int v2 = data[offset3++] & 0xff;
data[offset2++] = (byte)((v1 + v2) >> 1);
}
y -= 2;
}
// (3) copy second row of scaled image to first row
int x1 = 0;
int x2 = newWidth;
while (x1 < newWidth)
{
data[x1++] = data[x2++];
}
}
}
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