撕衣服小案例

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //[1]找到iv 显示我们操作的图片 
        final ImageView iv = (ImageView) findViewById(R.id.iv);
        
        //[2]把我们要操作的图片转换成bitmap
        Bitmap srcBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.pre19);
        
        //[3]创建原图的副本  
        
        //[3.1]创建模板
        final Bitmap alterbBitmap = Bitmap.createBitmap(srcBitmap.getWidth(), srcBitmap.getHeight(), srcBitmap.getConfig());
        //[3.2]以alterbBitmap bitmap为模板创建一个画布 
        Canvas canvas = new Canvas(alterbBitmap);
        //[3.3]创建一个画笔 
        Paint paint = new Paint();
        //[3.4]开始作画 
        canvas.drawBitmap(srcBitmap, new Matrix(), paint);
        
        //[4]把alterbitmap显示到iv上 
        iv.setImageBitmap(alterbBitmap);
        
        //[5]给iv设置一个触摸事件 
        iv.setOnTouchListener(new OnTouchListener() {
            
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                //[6]获取触摸事件的类型 
                int action = event.getAction();
                switch (action) {
                    
                case MotionEvent.ACTION_MOVE: //移动  
                    
                    for (int i = -7; i < 7; i++) {  //改变x 
                        
                        for (int j = -7; j <7; j++) {
                            //为了 良好的用户体验 撕一个圆 
                            if (Math.sqrt(i*i+j*j)<7) {
                                //一次修改一个像素 
                                try {
                                    alterbBitmap.setPixel((int)event.getX()+i, (int)event.getY()+j, Color.TRANSPARENT);
                                } catch (Exception e) {
                                }
                            }
                            
                            
                        }
                        
                    }
                
                    
                    //一定要记得更新iv
                    iv.setImageBitmap(alterbBitmap);
                    break;

                }
                
                return true;
            }
        });
        
        
        
    }

}