Android: 缩放图片文件引起的OOM异常_thumbnails oom-优快云博客

本文介绍了如何通过设置缩放选项和读取缩放后的图片数据来避免内存溢出（OOM）问题，以实现高效图片缩放与存储。以MMS应用为例，详细阐述了其在处理多媒体附件时对图片进行缩放的方法，包括获取原始图片尺寸、设置缩放选项、读取缩放图片数据并保存为文件等步骤。

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传输文件，或者设置头像，我们一般都会检查原始图片的大小，作缩放处理。

常用的Java版缩放图片代码：

 
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 public Bitmap getZoomImage(Bitmap src, int desW, int desH)  
 {  
     Bitmap desImg =  null;  
      int srcW = src.getWidth(); // 原始图像宽  
      int srcH = src.getHeight(); // 原始图像高  
      int[] srcBuf = new int[srcW * srcH]; // 原始图片像素信息缓存  
        
     src.getPixels(srcBuf,  0, srcW, 0, 0, srcW, srcH);  
        
      // 计算插值表  
      int[] tabY = new int[desH];  
      int[] tabX = new int[desW];  
        
      int sb = 0;  
      int db = 0;  
      int tems = 0;  
      int temd = 0;  
      int distance = srcH > desH ? srcH : desH;  
      for (int i = 0; i <= distance; i++)  
     {/* 垂直方向 */  
         tabY[db] = sb;  
         tems += srcH;  
         temd += desH;  
          if (tems > distance)  
         {   
             tems -= distance;  
             sb++;  
         }   
          if (temd > distance)  
         {   
             temd -= distance;  
             db++;  
         }   
     }   
        
     sb =  0;   
     db =  0;   
     tems =  0;   
     temd =  0;   
     distance = srcW > desW ? srcW : desW;  
        
      for (int i = 0; i <= distance; i++)  
     {/* 水平方向 */  
         tabX[db] = (short) sb;  
         tems += srcW;  
         temd += desW;  
          if (tems > distance)  
         {   
             tems -= distance;  
             sb++;  
         }   
          if (temd > distance)  
         {   
             temd -= distance;  
             db++;  
         }   
     }   
        
      // 生成放大缩小后图形像素  
      int[] desBuf = new int[desW * desH];  
      int dx = 0;  
      int dy = 0;  
      int sy = 0;  
      int oldy = -1;  
        
      for (int i = 0; i < desH; i++)  
     {   
          if (oldy == tabY[i])  
         {   
             System.arraycopy(desBuf, dy - desW, desBuf, dy, desW);  
         }   
          else  
         {   
             dx =  0;   
              for (int j = 0; j < desW; j++)  
             {  
                 desBuf[dy + dx] = srcBuf[sy + tabX[j]];  
                 dx++;  
             }  
             sy += (tabY[i] - oldy) * srcW;  
         }   
         oldy = tabY[i];  
         dy += desW;  
     }   
      // 生成图片  
     desImg = Bitmap.createBitmap(desBuf, desW, desH, Bitmap.Config.ARGB_8888);  
        
      return desImg;  
 }  

常用的Android版缩放图片代码：

 
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 ContentResolver cr = this.getContentResolver();  
 try  
 {  
     InputStream in = cr.openInputStream(uri);  
     Bitmap bitmap = BitmapFactory.decodeStream(in);  
      try   
     {   
         in.close();  
     }   
      catch (IOException e)  
     {   
         e.printStackTrace();  
     }   
      if(null  == bitmap)  
     {   
         Toast.makeText(this, "Head is not set successful,Decode bitmap failure", 2000);  
     }   
      //原始图片的尺寸  
      int bmpWidth  = bitmap.getWidth();  
      int bmpHeight = bitmap.getHeight();  
        
      //缩放图片的尺寸  
      float scaleWidth  = (float) 40 / bmpWidth;  
      float scaleHeight = (float) 40 / bmpHeight;  
     Matrix matrix =  new Matrix();  
     matrix.postScale(scaleWidth, scaleHeight);  
        
      //产生缩放后的Bitmap对象  
     Bitmap resizeBitmap = Bitmap.createBitmap(  
         bitmap,  0,  0, bmpWidth, bmpHeight, matrix, false);  
     bitmap.recycle();  
      //Bitmap to byte[]  
      byte[] photoData = Bitmap2Bytes(resizeBitmap);  
        
      //save file  
     String fileName =  "/sdcard/test.jpg";  
     FileUtil.writeToFile(fileName, photoData);  
        
      //save photo check sum to db  
     DataCenter.GetInstance().ModifyIMMUser();  
      //refresh ImageView  
 }  
 catch (FileNotFoundException exp)  
 {  
     exp.printStackTrace();  
 }  

如果图片非常大，在执行BitmapFactory.decodeStream的时候就会抛出OOM异常。

我们来看看系统应用MMS是如何处理的，SMS添加了多媒体附件后就作MMS处理了，当附加文件原图超过300K，也会做个缩放处理，具体参考：com.android.mms.ui/.UriImage：

 
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 package com.android.mms.ui;  
 public class UriImage  
 {  
      private int mWidth;  
      private int mHeight;  
     ... ...  
      //   
      private void decodeBoundsInfo()  
     {   
         InputStream input =  null;  
          try   
         {   
             input = mContext.getContentResolver().openInputStream(mUri);  
             BitmapFactory.Options opt =  new BitmapFactory.Options();  
             opt.inJustDecodeBounds =  true;//只描边，不读取数据  
             BitmapFactory.decodeStream(input,  null, opt);  
             mWidth = opt.outWidth;  
             mHeight = opt.outHeight;  
         }   
          catch (FileNotFoundException e)  
         {   
              // Ignore  
             Log.e(TAG,  "IOException caught while opening stream", e);  
         }   
          finally  
         {   
              if (null != input) {  
                  try {  
                     input.close();  
                 }  catch (IOException e) {  
                      // Ignore  
                     Log.e(TAG,  "IOException caught while closing stream", e);  
                 }  
             }  
         }   
     }   
      private byte[] getResizedImageData(int widthLimit, int heightLimit)  
     {   
          int outWidth = mWidth;  
          int outHeight = mHeight;  
          int s = 1;  
          while ((outWidth / s > widthLimit) || (outHeight / s > heightLimit))  
         {   
             s *=  2;   
         }   
          //先设置选项  
         BitmapFactory.Options options =  new BitmapFactory.Options();  
          //returning a smaller image to save memory.  
         options.inSampleSize = s;  
         InputStream input =  null;  
          try   
         {   
             input = mContext.getContentResolver().openInputStream(mUri);  
             Bitmap b = BitmapFactory.decodeStream(input,  null, options);//注意看options的用法  
              if (b == null) {  
                  return null;  
             }  
             ByteArrayOutputStream os =  new ByteArrayOutputStream();  
             b.compress(CompressFormat.JPEG, MessageUtils.IMAGE_COMPRESSION_QUALITY, os);  
              return os.toByteArray();  
         }  catch (FileNotFoundException e) {  
             Log.e(TAG, e.getMessage(), e);  
              return null;  
         }  finally {  
              if (input != null) {  
                  try {  
                     input.close();  
                 }  catch (IOException e) {  
                     Log.e(TAG, e.getMessage(), e);  
                 }  
             }  
         }   
     }   
     ... ...  
 }  

可以看出，MMS应用的方法是：先设置缩放选项，再读取缩放的图片数据到内存，规避了内存引起的OOM。

修改后的代码：

 
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     ContentResolver cr = this.getContentResolver();  
      try   
     {   
         InputStream in = cr.openInputStream(uri);  
            BitmapFactory.Options options =  new BitmapFactory.Options();  
            options.inJustDecodeBounds =  true;  
            BitmapFactory.decodeStream(in,  null, options);  
          try   
         {   
     in.close();  
 }  
          catch (IOException e)  
         {   
     e.printStackTrace();  
 }  
             int mWidth = options.outWidth;  
             int mHeight = options.outHeight;  
              
             int sWidth  = 40;  
             int sHeight = 40;  
              
          int s = 1;  
          while ((mWidth / s > sWidth * 2) || (mHeight / s > sHeight * 2))  
         {   
             s *=  2;   
         }   
            options =  new BitmapFactory.Options();  
         options.inSampleSize = s;  
         in = cr.openInputStream(uri);  
         Bitmap bitmap = BitmapFactory.decodeStream(in,  null, options);  
          try   
         {   
     in.close();  
 }  
          catch (IOException e)  
         {   
     e.printStackTrace();  
 }  
          if(null  == bitmap)  
         {   
             Toast.makeText(this, "Head is not set successful,Decode bitmap failure", 2000);  
              return ;  
         }   
          //原始图片的尺寸  
          int bmpWidth  = bitmap.getWidth();  
          int bmpHeight = bitmap.getHeight();  
            
          //缩放图片的尺寸  
          float scaleWidth  = (float) sWidth / bmpWidth;  
          float scaleHeight = (float) sHeight / bmpHeight;  
         Matrix matrix =  new Matrix();  
         matrix.postScale(scaleWidth, scaleHeight);  
            
          //产生缩放后的Bitmap对象  
         Bitmap resizeBitmap = Bitmap.createBitmap(  
             bitmap,  0,  0, bmpWidth, bmpHeight, matrix, false);  
         bitmap.recycle();  
                 Bitmap resizeBitmap = bitmap;  
          //Bitmap to byte[]  
          byte[] photoData = bitmap2Bytes(resizeBitmap);  
            
          //save file  
         String fileName =  "/sdcard/test.jpg";  
         FileUtil.writeToFile(fileName, photoData);  

 
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 private byte[] bitmap2Bytes(Bitmap bm)  
 {  
     ByteArrayOutputStream baos =  new ByteArrayOutputStream();  
     bm.compress(Bitmap.CompressFormat.JPEG,  100, baos);  
      return baos.toByteArray();  
 }  