Canvas提供了一个方法
drawBitmapMesh(Bitmap bitmap, int meshWidth, int meshHeight, class="tags" href="/tags/FLOAT.html" title=float>float[] verts, int vertOffset, int[] class="tags" href="/tags/COLORS.html" title=colors>colors,int colorffset,Paint paint) 
这个方法可以对bitmap进行扭曲
参数说明如下:
bitmap　　　　　需要扭曲的源位图
meshWidth 　　控制在横向上把该源位图划成成多少格
meshHeight 　　控制在纵向上把该源位图划成成多少格 
verts 　　　　　长度为(meshWidth + 1) * (meshHeight + 1) * 2的数组，它记录了扭曲后的位图各顶点位置
vertOffset         控制verts数组中从第几个数组元素开始才对bitmap进行扭曲

下面是扭曲一张风景图片的例子

class="language-java">package WangLi.Graphics.WarpTest;

import class="tags" href="/tags/ANDROID.html" title=android>android.app.Activity;
import class="tags" href="/tags/ANDROID.html" title=android>android.content.Context;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Bitmap;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.BitmapFactory;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Canvas;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Color;
import class="tags" href="/tags/ANDROID.html" title=android>android.os.Bundle;
import class="tags" href="/tags/ANDROID.html" title=android>android.util.AttributeSet;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.MotionEvent;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View;

public class WarpTest extends Activity {
    /** Called when the activity is first created. */
    private Bitmap bitmap;
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this,R.drawable.psb));
    }
	private class MyView extends View
	{
		//定义两个常量,这两个常量指定该图片横向,纵向上都被划分为20格
		private final int WIDTH = 20;
		private final int HEIGHT = 20;
		//记录该图片上包含441个顶点
		private final int COUNT = (WIDTH + 1) * (HEIGHT + 1); 
		//定义一个数组,记录Bitmap上的21*21个点的坐标
		private final class="tags" href="/tags/FLOAT.html" title=float>float[] verts = new class="tags" href="/tags/FLOAT.html" title=float>float[COUNT * 2];
		//定义一个数组,记录Bitmap上的21*21个点经过扭曲后的坐标
		//对图片扭曲的关键就是修改该数组里元素的值
		private final class="tags" href="/tags/FLOAT.html" title=float>float[] orig = new class="tags" href="/tags/FLOAT.html" title=float>float[COUNT * 2];
		public MyView(Context context, int drawableId) {
			super(context);
			setFocusable(true);
			//根据指定资源加载图片
			bitmap = BitmapFactory.decodeResource(getResources(), drawableId);
			//获取图片宽度和高度
			class="tags" href="/tags/FLOAT.html" title=float>float bitmapWidth = bitmap.getWidth();
			class="tags" href="/tags/FLOAT.html" title=float>float bitmapHeight = bitmap.getHeight();
			int index = 0;
			for(int y = 0; y <= HEIGHT; y++)
			{
				class="tags" href="/tags/FLOAT.html" title=float>float fy = bitmapHeight * y / HEIGHT;
				for(int x = 0 ; x <= WIDTH; x++)
				{
					class="tags" href="/tags/FLOAT.html" title=float>float fx = bitmapWidth * x / WIDTH;
					//初始化orig,verts数组
					//初始化,orig,verts两个数组均匀地保存了21 * 21个点的x,y坐标　
					orig[index * 2 + 0] = verts[index * 2 + 0] = fx;
					orig[index * 2 + 1] = verts[index * 2 + 1] = fy;
					index += 1;
				}
			}
			//设置背景色 
			setBackgroundColor(Color.WHITE);
		}
		protected void onDraw(Canvas canvas)
		{
			//对bitmap按verts数组进行扭曲
			//从第一个点(由第5个参数0控制)开始扭曲
			canvas.drawBitmapMesh(bitmap, WIDTH, HEIGHT, verts, 0, null, 0, null);
		}
		//工具方法,用于根据触摸事件的位置计算verts数组里各元素的值
		private void warp(class="tags" href="/tags/FLOAT.html" title=float>float cx, class="tags" href="/tags/FLOAT.html" title=float>float cy)
		{
			for(int i = 0; i < COUNT * 2; i += 2)
			{
				class="tags" href="/tags/FLOAT.html" title=float>float dx = cx - orig[i + 0];
				class="tags" href="/tags/FLOAT.html" title=float>float dy = cy - orig[i + 1];
				class="tags" href="/tags/FLOAT.html" title=float>float dd = dx * dx + dy * dy;
				//计算每个坐标点与当前点(cx,cy)之间的距离
				class="tags" href="/tags/FLOAT.html" title=float>float d = (class="tags" href="/tags/FLOAT.html" title=float>float)Math.sqrt(dd);
				//计算扭曲度，距离当前点(cx,cy)越远，扭曲度越小
				class="tags" href="/tags/FLOAT.html" title=float>float pull = 80000 / ((class="tags" href="/tags/FLOAT.html" title=float>float)(dd * d));
				//对verts数组(保存bitmap　上21 * 21个点经过扭曲后的坐标)重新赋值
				if(pull >= 1)
				{
					verts[i + 0] = cx;
					verts[i + 1] = cy;
				}
				else
				{
					//控制各顶点向触摸事件发生点偏移
					verts[i + 0] = orig[i + 0] + dx * pull;
					verts[i + 1] = orig[i + 1] + dx * pull;
				}
			}
			//通知View组件重绘
			invalidate();
		}
		public boolean onTouchEvent(MotionEvent event)
		{
			//调用warp方法根据触摸屏事件的坐标点来扭曲verts数组
			warp(event.getX() , event.getY());
			return true;
		}
	}
}