Android drawBitmapMesh扭曲触摸点的图像

Parameters
bitmap Bitmap: The bitmap to draw using the mesh
meshWidth int: The number of columns in the mesh. Nothing is drawn if this is 0
meshHeight int: The number of rows in the mesh. Nothing is drawn if this is 0
verts float: Array of x,y pairs, specifying where the mesh should be drawn. There must be at least (meshWidth+1) * (meshHeight+1) * 2 + vertOffset values in the array
vertOffset int: Number of verts elements to skip before drawing
colors int: May be null. Specifies a color at each vertex, which is interpolated across the cell, and whose values are multiplied by the corresponding bitmap colors. If not null, there must be at least (meshWidth+1) * (meshHeight+1) + colorOffset values in the array.
colorOffset int: Number of color elements to skip before drawing
paint Paint: May be null. The paint used to draw the bitmap

public class MainActivity extends Activity {
    private Bitmap bitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(MainActivity.this, R.drawable.jinta));
    }
    private class MyView extends View{
        //将图片在横向，纵向划分为20格
        private final int WIDTH=20,HEIGHT=20;
        //包含441个顶点
        private final int COUNT=(WIDTH+1)*(HEIGHT+1);
        //保存原坐标
        private final float[] verts=new float[COUNT*2];
        //保存扭曲后坐标，对图片扭曲关键为修改该数组的值
        private final float[] orig=new float[COUNT*2];

        public MyView(Context context,int DrawableId) {
            super(context);
            setFocusable(true);
            //加载图片资源
            bitmap=BitmapFactory.decodeResource(getResources(), DrawableId);
            //获取高，宽
            float bitmapWidth=bitmap.getWidth(),
                    bitmapHeight=bitmap.getHeight();
            int index=0;
            //对原坐标和扭曲后坐标数组进行初始化操作
            for(int y=0;y<=HEIGHT;y++){
                float fy=bitmapHeight*y/HEIGHT;
                for(int x=0;x<=WIDTH;x++){
                    float fx=bitmapWidth*x/WIDTH;
                    orig[index*2+0]=verts[index*2+0]=fx;
                    orig[index*2+1]=verts[index*2+1]=fy;
                    index+=1;
                }
            }
            //背景色
            setBackgroundColor(Color.WHITE);
        }
        @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawBitmapMesh(bitmap,WIDTH,HEIGHT,verts,0,null,0,null);
        }
        //cx,cy为touch事件发生坐标
        private void wrap(float cx,float cy){
            for(int i=0;i<COUNT*2;i+=2){
                //dx，dy为当前点距离事件发生点的坐标差
                float dx=cx-orig[i+0];
                float dy=cy-orig[i+1];
                float dd=dx*dx+dy*dy;
                //d为当前点与事件发生点的距离
                float d=(float)Math.sqrt(dd);
                //pull为扭曲度，距离越大扭曲程度越小
                float pull=80000/((float)(dd*d));
                if(pull>=1){
                    //距离近，直接扭曲至事件发生点
                    verts[i+0]=cx;
                    verts[i+1]=cy;
                }else{
                    //距离稍远，向事件发生偏移
                    verts[i+0]=orig[i+0]+dx*pull;
                    verts[i+1]=orig[i+1]+dy*pull;
                }
            }
            //通知组件调用OnDraw重绘
            invalidate();
        }
        @Override
        public boolean onTouchEvent(MotionEvent event) {
            //触摸事件发生时调用扭曲方法
            wrap(event.getX(),event.getY());
            return true;
        }
    }
}