当前位置: 代码迷 >> Android >> Android Bit地图 与 Drawable之间的区别和转换
  详细解决方案

Android Bit地图 与 Drawable之间的区别和转换

热度:85   发布时间:2016-04-28 06:31:33.0
Android Bitmap 与 Drawable之间的区别和转换

 Bitmap - 称作位图,一般位图的文件格式后缀为bmp,当然编码器也有很多如RGB565、RGB888。作为一种逐像素的显示对象执行效率高,但是缺点也很明显存储效率低。我们理解为一种存储对象比较好。
    Drawable - 作为Android平下通用的图形对象,它可以装载常用格式的图像,比如GIF、PNG、JPG,当然也支持BMP,当然还提供一些高级的可视化对象,比如渐变、图形等。

A bitmap is a Drawable. A Drawable is not necessarily a bitmap. Like all thumbs are fingers but not all fingers are thumbs.
Bitmap是Drawable . Drawable不一定是Bitmap .就像拇指是指头,但不是所有的指头都是拇指一样.

The API dictates: API规定:

Though usually not visible to the application, Drawables may take a variety of forms: 尽管通常情况下对于应用是不可见的,Drawables 可以采取很多形式:

Bitmap: the simplest Drawable, a PNG or JPEG image. Bitmap: 简单化的Drawable, PNG 或JPEG图像.
Nine Patch: an extension to the PNG format allows it to specify information about how to stretch it and place things inside of it.
Shape: contains simple drawing commands instead of a raw bitmap, allowing it to resize better in some cases.
Layers: a compound drawable, which draws multiple underlying drawables on top of each other.
States: a compound drawable that selects one of a set of drawables based on its state.
Levels: a compound drawable that selects one of a set of drawables based on its level.
Scale: a compound drawable with a single child drawable, whose overall size is modified based on the current level.

小结:

对比项          显示清晰度      占用内存     支持缩放    支持色相色差调整      支持旋转     支持透明色       绘制速度           支持像素操作

Bitmap          相同                大                 是                是                            是                是                     慢                      是
Drawable       相同                小                 是               否                            是                 是                     快                      否


Drawable在内存占用和绘制速度这两个非常关键的点上胜过Bitmap

//转换Bitmap to DrawableBitmap bitmap = new Bitmap (...);Drawable drawable = new BitmapDrawable(bitmap); //转换Drawable to BitmapDrawable d = ImagesList.get(0);Bitmap bitmap = ((BitmapDrawable)d).getBitmap();  //1、Drawable → Bitmappublic static Bitmap drawableToBitmap(Drawable drawable) {                  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);        return bitmap;} //2、从资源中获取BitmapResources res=getResources();Bitmap bmp=BitmapFactory.decodeResource(res, R.drawable.pic); //3、Bitmap → byte[]private byte[] Bitmap2Bytes(Bitmap bm){    ByteArrayOutputStream baos = new ByteArrayOutputStream();    bm.compress(Bitmap.CompressFormat.PNG, 100, baos);    return baos.toByteArray();   } //4、 byte[] → Bitmapprivate Bitmap Bytes2Bimap(byte[] b){            if(b.length!=0){                return BitmapFactory.decodeByteArray(b, 0, b.length);            }            else {                return null;            }      }


  相关解决方案