使用drawBitmapMesh扭曲图片

实例

MainActivity.java

package com.example.drawbitmapmesh;

import android.os.Bundle;

import android.app.Activity;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Color;

import android.view.Menu;

import android.view.MotionEvent;

import android.view.View;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new MyView(MainActivity.this));
}

public class MyView extends View{

private Bitmap bitmap;

//指定图片横向，纵向被划分为20个格
private final int WIDTH=20;
private final int HEIGHT=20;

//定义顶点数量
private final int COUNT=(WIDTH+1)*(HEIGHT+1);

//定义一个数组，保存Bitmap上的21*21个点的坐标
private final float[] verts=new float[COUNT*2];

//顶一个数组，记录Bitmap未被扭曲之前的坐标
private final float[] orig=new float[COUNT*2];

public MyView(Context context) {
super(context);
bitmap=BitmapFactory.decodeResource(getResources(), R.drawable.my_img);
//获取图片的宽度和高度
float imageWidth=bitmap.getWidth();
float imageHeight=bitmap.getHeight();

int index=0;

for(int x=0;x<=WIDTH;x++){
float fx=(imageWidth/WIDTH)*x;
for(int y=0;y<=HEIGHT;y++){
float fy=(imageHeight/HEIGHT)*y;
orig[index*2+0]=verts[index*2+0]=fx;
orig[index*2+1]=verts[index*2+1]=fy;
index+=1;
}
}
setBackgroundColor(Color.WHITE);
}

//根据触摸位置计算verts数组里各元素的值
private void warp(float cx,float cy){
for(int i=0;i<COUNT*2;i+=2){
//获取触摸点和原始坐标x,y的距离
float dx=cx-orig[i];
float dy=cy-orig[i];

//计算触摸点和其他原始点的距离
float dd=dx*dx+dy*dy;
float d=(float) Math.sqrt(dd);

//计算扭曲度，距离当前点(cx,cy越远)扭曲度越小
float pull=200/d;
if(pull>=1){
verts[i+0]=cx;
verts[i+1]=cy;
}
else{
//控制各顶点向触摸事件发生偏移
verts[i+0]=orig[i+0]+dx*pull;
verts[i+1]=orig[i+1]+dy*pull;
}

}
invalidate();

}

@Override
protected void onDraw(Canvas canvas) {
//对Bitmap按verts数组进行扭曲
canvas.drawBitmapMesh(bitmap, WIDTH, HEIGHT, verts, 0, null, 0, null);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
//调用wrap方法，根据触摸屏时间的坐标来扭曲verts数组
warp(event.getX(), event.getY());
return true;
}

}

}