andriod.graphics.BitmapFactory类详解

约定不等于承诺〃 2022-08-26 01:00 111阅读 0赞

Bitmap实现在android.graphics包中。但是Bitmap类的构造函数是私有的，外面并不能实例化，只能是通过JNI实例化。这必然是 某个辅助类提供了创建Bitmap的接口，而这个类的实现通过JNI接口来实例化Bitmap的，这个类就是BitmapFactory

public class

# BitmapFactory #

extends Object

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   <td colspan="2" style="margin:0px; padding:0px; border:none; vertical-align:top; background-color:inherit"> <a style="color:rgb(0,102,153)" rel="nofollow">java.lang.Object</a></td> 
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   <td style="margin:0px; padding:0px; border:none; vertical-align:top; background-color:inherit; font-weight:bold; width:1em"> &nbsp;&nbsp;&nbsp;↳</td> 
   <td colspan="1" style="margin:0px; padding:0px; border:none; vertical-align:top; background-color:inherit"> android.graphics.BitmapFactory</td> 
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   <th colspan="12" style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:rgb(222,232,241)"> Public Methods</th> 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeByteArray</a></span>(byte[] data, int offset, int length,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode an immutable bitmap from the specified byte array. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeByteArray</a></span>(byte[] data, int offset, int length) <span style="color:#ff0000">从字节数组中解码出Bitmap</span> 
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      Decode an immutable bitmap from the specified byte array. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeFile</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">String</a>&nbsp;pathName) <span style="color:#ff0000">从文件路径解码出Bitmap</span> 
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      Decode a file path into a bitmap. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeFile</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">String</a>&nbsp;pathName,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) <span style="color:rgb(255,0,0); white-space:nowrap; background-color:rgb(246,246,246)">BitmapFactory.Options为解码参数</span> 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode a file path into a bitmap. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeFileDescriptor</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">FileDescriptor</a>&nbsp;fd) <span style="color:#ff0000">从一个文件描述符解码出Bitmap</span> 
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      Decode a bitmap from the file descriptor. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeFileDescriptor</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">FileDescriptor</a>&nbsp;fd,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Rect</a>&nbsp;outPadding,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) <span style="color:rgb(255,0,0); white-space:nowrap; background-color:rgb(246,246,246)">从一个文件描述符解码出Bitmap，<span style="color:rgb(255,0,0); white-space:nowrap; background-color:rgb(246,246,246)">以矩阵outPadding为大小，<br> BitmapFactory.Options为解码参数</span></span> 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode a bitmap from the file descriptor. 
    </div> </td> 
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  <tr style="margin:0px; padding:0px; border:0px; background-color:rgb(246,246,246)"> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeResource</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Resources</a>&nbsp;res, int id,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Synonym for opening the given resource and calling&nbsp; 
     <code style="color:rgb(0,112,0); line-height:1em"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeResourceStream(Resources, TypedValue, InputStream, Rect, BitmapFactory.Options)</a></code>. 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeResource</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Resources</a>&nbsp;res, int id) 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Synonym for&nbsp; 
     <code style="color:rgb(0,112,0); line-height:1em"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeResource(Resources, int, android.graphics.BitmapFactory.Options)</a></code>&nbsp;will null Options. 
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    <div style="margin:0px; padding:3px 1em 0px; border:0px"> 
     <span style="color:#ff0000">Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.pic180);</span> 
     <br> 
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   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeResourceStream</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Resources</a>&nbsp;res,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">TypedValue</a>&nbsp;value,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">InputStream</a>&nbsp;is,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Rect</a>&nbsp;pad,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode a new Bitmap from an InputStream. 
    </div> </td> 
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  <tr style="margin:0px; padding:0px; border:0px"> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeStream</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">InputStream</a>&nbsp;is) 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode an input stream into a bitmap. 
    </div> </td> 
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  <tr style="margin:0px; padding:0px; border:0px; background-color:rgb(246,246,246)"> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); text-align:right; vertical-align:top; background-color:inherit"> static&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Bitmap</a> </td> 
   <td style="margin:0px; padding:6px 12px; border:1px solid rgb(204,204,204); vertical-align:top; background-color:inherit"> <span style="margin-right:2px"><a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">decodeStream</a></span>( <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">InputStream</a>&nbsp;is,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">Rect</a>&nbsp;outPadding,&nbsp; <a style="color:rgb(0,102,153); text-decoration:none" rel="nofollow">BitmapFactory.Options</a>&nbsp;opts) <span style="color:#ff0000">从inputStream中解码出Bitmap，以矩阵outPadding为大小，<br> BitmapFactory.Options为解码参数</span> 
    <div style="margin:0px; padding:3px 1em 0px; border:0px">
      Decode an input stream into a bitmap. 
    </div> </td> 
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BitmapFactory.Options

public BitmapinBitmap  
public intinDensity  
public booleaninDither  
public booleaninInputShareable  
public booleaninJustDecodeBounds 如果设置为true，并不会把图像的数据完全解码，亦即decodeXyz()返回值为null，但是Options的outAbc中解出了图像的基本信息。  
public booleaninMutable  
public booleaninPreferQualityOverSpeed  
public Bitmap.ConfiginPreferredConfig 指定decode到内存中，手机中所采用的编码，可选值定义在Bitmap.Config中。缺省值是ARGB\_8888。  
public booleaninPurgeable  
public intinSampleSize 设置decode时的缩放比例  
public booleaninScaled  
public intinScreenDensity  
public intinTargetDensity  
public byte\[\]inTempStorage  
public booleanmCancel  
public intoutHeight 指定解码出来的高度  
public StringoutMimeType 指定解码出来的MimeType  
public intoutWidth 指定解码出来的宽度

2、Bitmap bitmap=bitmapDrawable.getBitmap();

二、// 转换为BitmapDrawable对象  
1、BitmapDrawable bmpDraw=new BitmapDrawable(bitmap);  
2、BitmapDrawable bitmapDrawable=new BitmapDrawable(InputStream);  
3、BitmapDrawable bmpDraw=(BitmapDrawable)getResources().getDrawable(R.drawable.pic180);