Android Studio——Android Bitmap开发之旅--基本操作

原文链接：http://blog.csdn.net/weihan1314/article/details/8012283

1 Bitmap加载方式

在介绍Bitmap--OOM 异常时，首先介绍一下Bitmap有哪几种加载方式。通常Bitmap的加载方式有Resource资源加载、本地（SDcard）加载、网络加载等加载方式。

1.1 Resource资源加载

1. Assets资源加载方式：
   

    AssetManager am = getAssets();
    InputStream is = am.open("high_pixel_img.jpg");
    Bitmap bitmap = BitmapFactory.decodeStream(is);

2.  Res资源加载方式：
   

    Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.high_pixel_img);

1.2 本地（SDcard）加载

 String file_name = Environment.getExternalStorageDirectory().toString()+"/"+"high_pixel_img.jpg";
 nbsp;Bitmap bitmap = BitmapFactory.decodeFile(file_name);

文件描述符

1.3 网络加载

注意：网络加载图片的时候必须在非主线成中操作

 String website = "http://www.baidu.com/img/baidu_sylogo1.gif";
 URL image_url = new URL(website);
 HttpURLConnection conn = (HttpURLConnection) image_url.openConnection();
 conn.connect();
 InputStream is = conn.getInputStream();
 bitmap = BitmapFactory.decodeStream(is);

2 Bitmap | Drawable | InputStream | Byte[ ] 之间进行转换

2.1 Drawable转化成Bitmap

 Drawable drawable = getResources().getDrawable(R.drawable.ic_launcher);
 Bitmap bitmap = Bitmap.createBitmap(
                                drawable.getIntrinsicWidth(),
                                drawable.getIntrinsicHeight(),
                                drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
                                                : Bitmap.Config.RGB_565);
 Canvas canvas = new Canvas(bitmap);
 //canvas.setBitmap(bitmap);
 drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
 drawable.draw(canvas);

2. 2 Bitmap转换成Drawable

 Drawable drawable = new BitmapDrawable(bitmap);

2.3 Bitmap转换成byte[]

 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.high_pixel_img);
 ByteArrayOutputStream baos = new ByteArrayOutputStream();
 bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
 byte[] info = baos.toByteArray();

2.4 byte[]转换成Bitmap

 Bitmap bitmap = BitmapFactory.decodeByteArray(byte, 0, b.length);

2.5 InputStream转换成Bitmap

 InputStream is  = getResources().openRawResource(id);
 Bitmap bitmap = BitmaoFactory.decodeStream(is);

2.6 InputStream转换成byte[]

 InputStream is = getResources().openRawResource(id);//也可以通过其他方式接收一个InputStream对象
 ByteArrayOutputStream baos = new ByteArrayOutputStream();
 byte[] b = new byte[1024*2];
 int len = 0;
 while ((len = is.read(b, 0, b.length)) != -1)
 {
    baos.write(b, 0, len);
    baos.flush();
 }
 byte[] bytes = baos.toByteArray();

3 转换Bitmap大小

 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.high_pixel_img);
 Bitmap target = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
 Canvas canvas = new Canvas(tartget);
 canvas.scale(scale,scale);
 Paint paint = new Pain(Paint.FILTER_BITMAP_FLAG | Paint.DITHER_FLAG);
 canvas.drawBitmap(bitmap,0,0,paint);
 bitmap.recycle();

4 将Bitmap保存为本地文件

 String filename = "save.jpg";
 File file = new File(Environmnet.getExternalStorageDirectory,filename);
 try{
     OutputStream os  =  new FileOutputString(file);
     bitmap.compress(CompressFormat.JPEG,100,os);
 }catch(FileNotFoundException e){
    e.printStackTrace();
 }