Android Bitmap 与 Drawable之间的区别和转换-酷五问

Android Bitmap 与 Drawable之间的区别和转换

的有关信息介绍如下：

Android Bitmap 与 Drawable之间的区别和转换

Android bitmap和drawable的区别和转换如下：

1.bitmap 转换 drawable

Bitmap bitmap = new Bitmap(...); Drawable drawable = new BitmapDrawable(bitmap);

//Drawable drawable = new FastBitmapDrawable(bitmap);2.Drawable to Bitmap

BitmapDrawable, FastBitmapDrawable直接用getBitmap

b. 其他类型的Drawable用Canvas画到一个bitmap上

Canvas canvas = new Canvas(bitmap)

drawable.draw(canvas);

Drawable d = ImagesList.get(0); Bitmap bitmap = ((BitmapDrawable)d).getBitmap();区别如下：

1.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。

2.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。

另外还有如下相类似的格式：

Canvas - 名为画布，可以看作是一种处理过程，使用各种方法来管理Bitmap、GL或者Path路径，同时它可以配合Matrix矩阵类给图像做旋转、缩放等操作，同时Canvas类还提供了裁剪、选取等操作。

Paint - 可以把它看做一个画图工具，比如画笔、画刷。管理了每个画图工具的字体、颜色、样式。

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 Drawable

Bitmap bitmap = new Bitmap (...);

Drawable drawable = new BitmapDrawable(bitmap);

//转换Drawable to Bitmap

Drawable d = ImagesList.get(0);

Bitmap bitmap = ((BitmapDrawable)d).getBitmap();

//1、Drawable → Bitmap

public 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Bitmap

Resources 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[] → Bitmap

private Bitmap Bytes2Bimap(byte[] b){

if(b.length!=0){

return BitmapFactory.decodeByteArray(b, 0, b.length);

}

else {

return null;