缩放加载大图片

09-14 00:59:51.813: E/AndroidRuntime(2128): Caused by: java.lang.OutOfMemoryError

09-14 00:59:51.813: E/dalvikvm-heap(2128): Out of memory on a 30720012-byte allocation.

在Android下采用ARGB来表示颜色  每个像素占4byte

图片:2400*3200

手机:320*480 

宽缩放: 7  

高缩放: 6  

需要考虑的问题 (1)动态获取图片的分辨率 

               　　　 (2)动态获取手机分辨率 

 

public class MainActivity extends Activity {

    private ImageView iv;
    private int screenWidth;
    private int screenHeight;


    @SuppressWarnings("deprecation")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //[1]找到iv 显示加载图片 
        
        iv = (ImageView) findViewById(R.id.iv);
        
        //[2]获取手机的分辨率  获取windowmanager 实例 
        WindowManager wm  = (WindowManager) getSystemService(WINDOW_SERVICE);
        screenWidth = wm.getDefaultDisplay().getWidth();
        screenHeight = wm.getDefaultDisplay().getHeight();
        
        System.out.println("手机的宽和高:"+screenWidth+"---"+screenHeight);
        
        
        
        
    }

    
    //点击按钮  加载dog.jpg 这张图片
    @SuppressLint("SdCardPath")
    public void click(View v) {
        //[2]把dog.jpg 转换成bitmap  
        
        //创建bitmap工厂的配置参数 
        BitmapFactory.Options options = new Options();
        
        //返回一个null 没有bitmap   不去真正解析位图 但是能返回图片的一些信息(宽和高)
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile("/mnt/sdcard/dog.jpg",options);
        //[3]获取图片的宽和高  
        int imgWidth = options.outWidth;
        int imgHeight = options.outHeight;
        System.out.println("图片的宽:"+imgWidth+"-----"+imgHeight);
        
        //[4]计算缩放比 
        int scale = 1;  //我们定义的缩放比 
        int scalex =  imgWidth/screenWidth;
        int scaley = imgHeight /screenHeight;
        if (scalex >=scaley&&scalex > scale) {
            scale = scalex;
        }
        if (scaley > scalex && scaley>scale) {
            scale = scaley;
        }
        System.out.println("缩放比为:"+scale);
        
        
        //[5]按照缩放比显示图片 
        options.inSampleSize = scale;
        
        //[6]开始真正的解析位图 
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeFile("/mnt/sdcard/dog.jpg",options);
        
        //[7]把bitmap显示到控件上
        iv.setImageBitmap(bitmap);
        
        
        
        
    }
    

}