Android - 从磁盘上传图像

Question

我在 Android 上上传文件时遇到了一些问题。我已经将应用程序的这一部分拼凑在一起，现在需要进行一些修改。

我正在尝试从 Uri 引用的磁盘映像将文件上传到服务器。

在上传之前，我正在尝试根据纵横比将图像缩小到 1280 的最大尺寸。

这是一个示例类，其中包含我正在使用的实际代码。我敢肯定它的效率非常低：

/**
 * This is a fake class, this is actually spread across 2 or 3 files
 */
public class Temp
{
  /**
   * This is used to return an Input stream of known size
   */
  public static class KnownSizeInputStream extends InputStreamBody
  {
    private int mLength;

    public KnownSizeInputStream( final InputStream in, final int length, final String mimeType, final String filename )
    {
      super( in, mimeType, filename );
      mLength = length;
    }

    public long getContentLength()
    {
      return mLength;
    }
  }

  private static final int MAX_WIDTH  = 1280;
  private static final int MAX_HEIGHT = 1280;

  /**
   * Open up a file on disk and convert it into a stream of known size
   */
  public KnownSizeInputStream toStreamAio( Context c, Uri path )
  {
    /**
     * Scale down bitmap
     */
    Bitmap bitmapData = null;

    try
    {
      bitmapData = BitmapFactory.decodeStream( c.getContentResolver().openInputStream( path ) );
    }
    catch( Exception e )
    {
      e.printStackTrace();
    }

    int imgWidth = bitmapData.getWidth();
    int imgHeight = bitmapData.getHeight();

    // Constrain to given size but keep aspect ratio
    float scaleFactor = Math.min( ( ( float )MAX_WIDTH ) / imgWidth, ( ( float )MAX_HEIGHT ) / imgHeight );

    Matrix scale = new Matrix();
    scale.postScale( scaleFactor, scaleFactor );
    final Bitmap scaledImage = Bitmap.createBitmap( bitmapData, 0, 0, imgWidth, imgHeight, scale, false );

    try
    {
      bitmapData = scaledImage.copy( scaledImage.getConfig(), true );

      scaledImage.recycle();
    }
    catch( Exception e )
    {
      e.printStackTrace();
    }

    /**
     * To byte[]
     */
    byte[] byteData = null;

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

    bitmapData.compress( Bitmap.CompressFormat.JPEG, 100, baos );

    byteData = baos.toByteArray();

    /**
     * To stream
     */
    return new KnownSizeInputStream( new ByteArrayInputStream( byteData ), byteData.length, "image/jpg", "Some image" );
  }

  /** 
   * Some pieces are removed, the main part is the addPart line
   */
  public void doUpload()
  {
    // create a new HttpPost, to our specified URI
    HttpPost post = new HttpPost( postUri );

    // org.apache.http.entity.mime
    MultipartEntity entity = new MultipartEntity( HttpMultipartMode.STRICT );


    // This line starts all of the issues
    entity.addPart( "file", toStreamAio( mContext, Uri.parse( "/some/file.jpg" ) ) );


    post.setEntity( entity );

    // send it
    HttpResponse response = client.execute( post );

  }
}

这是我得到的例外，我猜测调整大小试图分配图像的完整大小：

Caused by: java.lang.OutOfMemoryError
 at android.graphics.Bitmap.nativeCopy(Native Method)
 at android.graphics.Bitmap.copy(Bitmap.java:403)
 at com.app.helper.UploadableImage.toScaledBitmap(UploadableImage.java:170)
 at com.app.helper.UploadableImage.toByteArray(UploadableImage.java:53)
 at com.app.helper.UploadableImage.toStream(UploadableImage.java:242)
 at com.app.rest.task.UploadContentTask.doInBackground(UploadContentTask.java:80)
 at com.app.rest.task.UploadContentTask.doInBackground(UploadContentTask.java:1)
 at android.os.AsyncTask$2.call(AsyncTask.java:264)
 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
 ... 5 more

它被这条线触发了：

data = scaledImage.copy( scaledImage.getConfig(), true );

我想我要问的主要问题是，如何从磁盘上的路径获取图像，到缩放的图像，再到可以放入的流：

org.apache.http.entity.mime.MultipartEntity

通过：

.addPart("file", streamData);

最有效的方法是，假设图像可以很大（~6000px 是我迄今为止达到的最大尺寸）

Answer 1

首先，为什么要复制缩放的位图？你不能像这样直接压缩缩放的位图吗：

final Bitmap scaledImage = Bitmap.createBitmap(bitmapData, 0, 0,
        imgWidth, imgHeight, scale, false);
scaledImage.compress(Bitmap.CompressFormat.JPEG, 100, baos);

如果您可以避免复制，则可以避免获得OutOfMemoryError。

此外，即使您使用 JPEG 压缩选择 95% 的质量（在处理自然物体的照片时），您也可以实现良好的压缩，而质量损失几乎无法察觉。您应该尝试质量设置并自行检查。

Answer 2

这是现在为我工作的完整课程。您使用 Context 和 Uri 加载它，然后调用三个公共方法中的任何一个：

public class UploadableImage
{
  private static final int MAX_WIDTH  = 1280;
  private static final int MAX_HEIGHT = 1280;

  private Uri              mUri;

  private String           mImageName;

  private Context          mContext;

  public UploadableImage( Context context )
  {
    mContext = context;

    generateFilename();
  }

  public UploadableImage( Context context, Uri uri )
  {
    mContext = context;
    mUri = uri;

    generateFilename();
  }

  // TODO Generate...
  private void generateFilename()
  {
    mImageName = UUID.randomUUID().toString() + ".jpg";
  }

  public void setUri( Uri uri )
  {
    mUri = uri;
  }

  public Bitmap toBitmap()
  {
    try
    {
      InputStream input = mContext.getContentResolver().openInputStream( mUri );

      BitmapFactory.Options readOptions = new BitmapFactory.Options();
      readOptions.inJustDecodeBounds = true;

      BitmapFactory.decodeStream( input, null, readOptions );

      input.close();

      // Raw height and width of image
      final int height = readOptions.outHeight;
      final int width = readOptions.outWidth;

      int inSampleSize = 1;

      if( height > MAX_HEIGHT || width > MAX_WIDTH )
      {
        if( width > height )
        {
          float result = ( float )height / ( float )MAX_HEIGHT;

          inSampleSize = ( int )FloatMath.ceil( result );
        }
        else
        {
          float result = ( float )width / ( float )MAX_WIDTH;

          inSampleSize = ( int )FloatMath.ceil( result );
        }
      }

      return toBitmap( inSampleSize );
    }
    catch( Exception e )
    {
      e.printStackTrace();
    }

    return null;
  }

  public Bitmap toBitmap( int sampleSize )
  {
    try
    {
      InputStream input = mContext.getContentResolver().openInputStream( mUri );

      input = mContext.getContentResolver().openInputStream( mUri );

      // Decode bitmap with inSampleSize set
      BitmapFactory.Options scaleOptions = new BitmapFactory.Options();

      scaleOptions.inJustDecodeBounds = false;
      scaleOptions.inSampleSize = sampleSize;

      Bitmap scaledBitmap = BitmapFactory.decodeStream( input, null, scaleOptions );

      input.close();

      return scaledBitmap;
    }
    catch( Exception e )
    {
      e.printStackTrace();
    }

    return null;
  }

  public KnownSizeInputStream toMimeStream()
  {
    Bitmap scaledBitmap = toBitmap();

    ByteArrayOutputStream stream = new ByteArrayOutputStream();

    scaledBitmap.compress( Bitmap.CompressFormat.JPEG, 95, stream );

    byte[] byteArray = stream.toByteArray();

    return new KnownSizeInputStream( new ByteArrayInputStream( byteArray ), byteArray.length, "image/jpg", mImageName );
  }

  public String toString()
  {
    return "UploadableImage, Uri: " + mUri;
  }
}