主要思想：

主要是利用三角正弦函数与余弦函数的变换效果，完成对像素的位移变换，产生

水纹效果，因为自然界中的水纹多少都是正弦波或者余弦波的叠加效果。

参数解析：

支持两个输入参数设置，一个是波长，表示像素位移的多少，另外一个是周期

表示正弦或者余弦函数的在像素中的变换周期。

关键程序解析：

计算位移与周期变化代码如下：

xoffset = (int)((double)wave * Math.sin(2.0 * Math.PI * (float)row / period));
yoffset = (int)((double)wave * Math.cos(2.0 * Math.PI * (float)col / period));

程序效果：

程序源代码:

package com.gloomyfish.filter.study;

import java.awt.image.BufferedImage;

public class WaterFilter extends AbstractBufferedImageOp {
	
	private double wave;
	private double period;
	
	public WaterFilter() {
		wave = 25.0;
		period = 128;
	}
	
	public void setPeriod(double period) {
		this.period = period;
	}
	
	public void setWave(double nWave) {
		this.wave = nWave;
	}

	@Override
	public BufferedImage filter(BufferedImage src, BufferedImage dest) {
		int width = src.getWidth();
        int height = src.getHeight();

        if ( dest == null )
        	dest = createCompatibleDestImage( src, null );

        int[] inPixels = new int[width*height];
        int[] outPixels = new int[width*height];
        Point[][] ssPixels = new Point[height][width];
        getRGB( src, 0, 0, width, height, inPixels );
        int index = 0, index2 = 0;
        int xoffset = 0, yoffset = 0;
        for(int row=0; row<height; row++) {
        	for(int col=0; col<width; col++) {
                xoffset = (int)((double)wave * Math.sin(2.0 * Math.PI * (float)row / period));
                yoffset = (int)((double)wave * Math.cos(2.0 * Math.PI * (float)col / period));
                xoffset = xoffset + col;
                yoffset = yoffset + row;
                if(xoffset < 0 || xoffset >=width) {
                	xoffset = 0;
                }
                if(yoffset < 0 || yoffset >=height) {
                	yoffset = 0;
                }
                
                // save the 2D coordinate newX, and newY
                ssPixels[row][col] = new Point(xoffset, yoffset); 
        	}
        }
        
        // coordinate 2D result and fill the pixels data.
        for(int row=0; row<height; row++) {
        	int ta = 0, tr = 0, tg = 0, tb = 0;
        	for(int col=0; col<width; col++) {
        		index = row * width + col;
        		index2 = ssPixels[row][col].getRow() * width + ssPixels[row][col].getCol();
        		ta = (inPixels[index2] >> 24) & 0xff;
                tr = (inPixels[index2] >> 16) & 0xff;
                tg = (inPixels[index2] >> 8) & 0xff;
                tb = inPixels[index2] & 0xff;
                outPixels[index] = (ta << 24) | (tr << 16) | (tg << 8) | tb;
        	}
        }
        setRGB( dest, 0, 0, width, height, outPixels );
        return dest;
	}
	
	class Point {
		private int x;
		private int y;
		
		public Point(int x, int y) {
			this.x = x;
			this.y = y;
		}
		
		public int getRow() {
			return this.y;
		}
		
		public int getCol() {
			return this.x;
		}
		
	}

}

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