我在一个文件中有一个大的位图(比如3888x2592)。现在,我想将位图大小调整为800x533,并将其保存到另一个文件中。 我通常通过调用bitmap来缩放位图。createBitmap方法,但它需要一个源位图作为第一个参数,我不能提供,因为加载原始图像到位图对象当然会超过内存(例如,见这里)。

我也不能读取位图,例如,BitmapFactory.decodeFile(文件,选项),提供BitmapFactory.Options。inSampleSize,因为我想把它调整到精确的宽度和高度。使用inSampleSize将位图大小调整为972x648(如果我使用inSampleSize=4)或778x518(如果我使用inSampleSize=5,这甚至不是2的幂)。

我还希望避免在第一步中使用inSampleSize读取图像,例如,在第一步中使用972x648,然后在第二步中将其大小调整为800x533,因为与直接调整原始图像的大小相比,质量会较差。

总结一下我的问题: 是否有一种方法来读取一个10MP或更多的大图像文件,并将其保存到一个新的图像文件,调整到一个特定的新宽度和高度,而不得到OutOfMemory异常?

我还尝试了BitmapFactory.decodeFile(文件,选项)和设置选项。out theight and Options。outidth值手动为800和533,但它不是这样工作的。


当前回答

我使用了这样的代码:

  String filePath=Environment.getExternalStorageDirectory()+"/test_image.jpg";
  BitmapFactory.Options options=new BitmapFactory.Options();
  InputStream is=new FileInputStream(filePath);
  BitmapFactory.decodeStream(is, null, options);
  is.close();
  is=new FileInputStream(filePath);
  // here w and h are the desired width and height
  options.inSampleSize=Math.max(options.outWidth/460, options.outHeight/288); //Max 460 x 288 is my desired...
  // bmp is the resized bitmap
  Bitmap bmp=BitmapFactory.decodeStream(is, null, options);
  is.close();
  Log.d(Constants.TAG, "Scaled bitmap bytes, "+bmp.getRowBytes()+", width:"+bmp.getWidth()+", height:"+bmp.getHeight());

我试过原始图像是1230 x 1230,得到的位图是330 x 330。 如果尝试2590 x 3849,我将得到OutOfMemoryError。

我跟踪了它,它仍然抛出OutOfMemoryError在行"BitmapFactory.decodeStream(is, null, options);",如果原始位图太大…

其他回答

下面是我使用的代码,在Android上解码内存中的大图像没有任何问题。我已经能够解码大于20MB的图像,只要我的输入参数在1024x1024左右。您可以将返回的位图保存到另一个文件中。下面这个方法是另一个方法,我也用它来缩放图像到一个新的位图。请随意使用此代码。

/*****************************************************************************
 * public decode - decode the image into a Bitmap
 * 
 * @param xyDimension
 *            - The max XY Dimension before the image is scaled down - XY =
 *            1080x1080 and Image = 2000x2000 image will be scaled down to a
 *            value equal or less then set value.
 * @param bitmapConfig
 *            - Bitmap.Config Valid values = ( Bitmap.Config.ARGB_4444,
 *            Bitmap.Config.RGB_565, Bitmap.Config.ARGB_8888 )
 * 
 * @return Bitmap - Image - a value of "null" if there is an issue decoding
 *         image dimension
 * 
 * @throws FileNotFoundException
 *             - If the image has been removed while this operation is
 *             taking place
 */
public Bitmap decode( int xyDimension, Bitmap.Config bitmapConfig ) throws FileNotFoundException
{
    // The Bitmap to return given a Uri to a file
    Bitmap bitmap = null;
    File file = null;
    FileInputStream fis = null;
    InputStream in = null;

    // Try to decode the Uri
    try
    {
        // Initialize scale to no real scaling factor
        double scale = 1;

        // Get FileInputStream to get a FileDescriptor
        file = new File( this.imageUri.getPath() );

        fis = new FileInputStream( file );
        FileDescriptor fd = fis.getFD();

        // Get a BitmapFactory Options object
        BitmapFactory.Options o = new BitmapFactory.Options();

        // Decode only the image size
        o.inJustDecodeBounds = true;
        o.inPreferredConfig = bitmapConfig;

        // Decode to get Width & Height of image only
        BitmapFactory.decodeFileDescriptor( fd, null, o );
        BitmapFactory.decodeStream( null );

        if( o.outHeight > xyDimension || o.outWidth > xyDimension )
        {
            // Change the scale if the image is larger then desired image
            // max size
            scale = Math.pow( 2, (int) Math.round( Math.log( xyDimension / (double) Math.max( o.outHeight, o.outWidth ) ) / Math.log( 0.5 ) ) );
        }

        // Decode with inSampleSize scale will either be 1 or calculated value
        o.inJustDecodeBounds = false;
        o.inSampleSize = (int) scale;

        // Decode the Uri for real with the inSampleSize
        in = new BufferedInputStream( fis );
        bitmap = BitmapFactory.decodeStream( in, null, o );
    }
    catch( OutOfMemoryError e )
    {
        Log.e( DEBUG_TAG, "decode : OutOfMemoryError" );
        e.printStackTrace();
    }
    catch( NullPointerException e )
    {
        Log.e( DEBUG_TAG, "decode : NullPointerException" );
        e.printStackTrace();
    }
    catch( RuntimeException e )
    {
        Log.e( DEBUG_TAG, "decode : RuntimeException" );
        e.printStackTrace();
    }
    catch( FileNotFoundException e )
    {
        Log.e( DEBUG_TAG, "decode : FileNotFoundException" );
        e.printStackTrace();
    }
    catch( IOException e )
    {
        Log.e( DEBUG_TAG, "decode : IOException" );
        e.printStackTrace();
    }

    // Save memory
    file = null;
    fis = null;
    in = null;

    return bitmap;

} // decode

注意:方法之间没有任何关系,除了createScaledBitmap调用上面的decode方法。注意宽度和高度可以改变原始图像。

/*****************************************************************************
 * public createScaledBitmap - Creates a new bitmap, scaled from an existing
 * bitmap.
 * 
 * @param dstWidth
 *            - Scale the width to this dimension
 * @param dstHeight
 *            - Scale the height to this dimension
 * @param xyDimension
 *            - The max XY Dimension before the original image is scaled
 *            down - XY = 1080x1080 and Image = 2000x2000 image will be
 *            scaled down to a value equal or less then set value.
 * @param bitmapConfig
 *            - Bitmap.Config Valid values = ( Bitmap.Config.ARGB_4444,
 *            Bitmap.Config.RGB_565, Bitmap.Config.ARGB_8888 )
 * 
 * @return Bitmap - Image scaled - a value of "null" if there is an issue
 * 
 */
public Bitmap createScaledBitmap( int dstWidth, int dstHeight, int xyDimension, Bitmap.Config bitmapConfig )
{
    Bitmap scaledBitmap = null;

    try
    {
        Bitmap bitmap = this.decode( xyDimension, bitmapConfig );

        // Create an empty Bitmap which will contain the new scaled bitmap
        // This scaled bitmap should be the size we want to scale the
        // original bitmap too
        scaledBitmap = Bitmap.createBitmap( dstWidth, dstHeight, bitmapConfig );

        float ratioX = dstWidth / (float) bitmap.getWidth();
        float ratioY = dstHeight / (float) bitmap.getHeight();
        float middleX = dstWidth / 2.0f;
        float middleY = dstHeight / 2.0f;

        // Used to for scaling the image
        Matrix scaleMatrix = new Matrix();
        scaleMatrix.setScale( ratioX, ratioY, middleX, middleY );

        // Used to do the work of scaling
        Canvas canvas = new Canvas( scaledBitmap );
        canvas.setMatrix( scaleMatrix );
        canvas.drawBitmap( bitmap, middleX - bitmap.getWidth() / 2, middleY - bitmap.getHeight() / 2, new Paint( Paint.FILTER_BITMAP_FLAG ) );
    }
    catch( IllegalArgumentException e )
    {
        Log.e( DEBUG_TAG, "createScaledBitmap : IllegalArgumentException" );
        e.printStackTrace();
    }
    catch( NullPointerException e )
    {
        Log.e( DEBUG_TAG, "createScaledBitmap : NullPointerException" );
        e.printStackTrace();
    }
    catch( FileNotFoundException e )
    {
        Log.e( DEBUG_TAG, "createScaledBitmap : FileNotFoundException" );
        e.printStackTrace();
    }

    return scaledBitmap;
} // End createScaledBitmap

我使用了这样的代码:

  String filePath=Environment.getExternalStorageDirectory()+"/test_image.jpg";
  BitmapFactory.Options options=new BitmapFactory.Options();
  InputStream is=new FileInputStream(filePath);
  BitmapFactory.decodeStream(is, null, options);
  is.close();
  is=new FileInputStream(filePath);
  // here w and h are the desired width and height
  options.inSampleSize=Math.max(options.outWidth/460, options.outHeight/288); //Max 460 x 288 is my desired...
  // bmp is the resized bitmap
  Bitmap bmp=BitmapFactory.decodeStream(is, null, options);
  is.close();
  Log.d(Constants.TAG, "Scaled bitmap bytes, "+bmp.getRowBytes()+", width:"+bmp.getWidth()+", height:"+bmp.getHeight());

我试过原始图像是1230 x 1230,得到的位图是330 x 330。 如果尝试2590 x 3849,我将得到OutOfMemoryError。

我跟踪了它,它仍然抛出OutOfMemoryError在行"BitmapFactory.decodeStream(is, null, options);",如果原始位图太大…

上面的代码更简洁一些。InputStreams最终关闭了包装,以确保它们也被关闭:

*请注意 输入:InputStream is, int w, int h 输出:位图

    try
    {

        final int inWidth;
        final int inHeight;

        final File tempFile = new File(temp, System.currentTimeMillis() + is.toString() + ".temp");

        {

            final FileOutputStream tempOut = new FileOutputStream(tempFile);

            StreamUtil.copyTo(is, tempOut);

            tempOut.close();

        }



        {

            final InputStream in = new FileInputStream(tempFile);
            final BitmapFactory.Options options = new BitmapFactory.Options();

            try {

                // decode image size (decode metadata only, not the whole image)
                options.inJustDecodeBounds = true;
                BitmapFactory.decodeStream(in, null, options);

            }
            finally {
                in.close();
            }

            // save width and height
            inWidth = options.outWidth;
            inHeight = options.outHeight;

        }

        final Bitmap roughBitmap;

        {

            // decode full image pre-resized
            final InputStream in = new FileInputStream(tempFile);

            try {

                final BitmapFactory.Options options = new BitmapFactory.Options();
                // calc rought re-size (this is no exact resize)
                options.inSampleSize = Math.max(inWidth/w, inHeight/h);
                // decode full image
                roughBitmap = BitmapFactory.decodeStream(in, null, options);

            }
            finally {
                in.close();
            }

            tempFile.delete();

        }

        float[] values = new float[9];

        {

            // calc exact destination size
            Matrix m = new Matrix();
            RectF inRect = new RectF(0, 0, roughBitmap.getWidth(), roughBitmap.getHeight());
            RectF outRect = new RectF(0, 0, w, h);
            m.setRectToRect(inRect, outRect, Matrix.ScaleToFit.CENTER);
            m.getValues(values);

        }

        // resize bitmap
        final Bitmap resizedBitmap = Bitmap.createScaledBitmap(roughBitmap, (int) (roughBitmap.getWidth() * values[0]), (int) (roughBitmap.getHeight() * values[4]), true);

        return resizedBitmap;

    }
    catch (IOException e) {

        logger.error("Error:" , e);
        throw new ResourceException("could not create bitmap");

    }

我不知道我的解决方案是否是最佳实践,但我通过使用inDensity和inTargetDensity选项实现了加载我所需缩放的位图。当不加载可绘制资源时,inDensity初始值为0,因此此方法用于加载非资源图像。

变量imageUri, maxImageSideLength和context是我的方法的参数。为了清晰起见,我只发布了方法实现,没有包装AsyncTask。

            ContentResolver resolver = context.getContentResolver();
            InputStream is;
            try {
                is = resolver.openInputStream(imageUri);
            } catch (FileNotFoundException e) {
                Log.e(TAG, "Image not found.", e);
                return null;
            }
            Options opts = new Options();
            opts.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(is, null, opts);

            // scale the image
            float maxSideLength = maxImageSideLength;
            float scaleFactor = Math.min(maxSideLength / opts.outWidth, maxSideLength / opts.outHeight);
            // do not upscale!
            if (scaleFactor < 1) {
                opts.inDensity = 10000;
                opts.inTargetDensity = (int) ((float) opts.inDensity * scaleFactor);
            }
            opts.inJustDecodeBounds = false;

            try {
                is.close();
            } catch (IOException e) {
                // ignore
            }
            try {
                is = resolver.openInputStream(imageUri);
            } catch (FileNotFoundException e) {
                Log.e(TAG, "Image not found.", e);
                return null;
            }
            Bitmap bitmap = BitmapFactory.decodeStream(is, null, opts);
            try {
                is.close();
            } catch (IOException e) {
                // ignore
            }

            return bitmap;
 Bitmap yourBitmap;
 Bitmap resized = Bitmap.createScaledBitmap(yourBitmap, newWidth, newHeight, true);

or:

 resized = Bitmap.createScaledBitmap(yourBitmap,(int)(yourBitmap.getWidth()*0.8), (int)(yourBitmap.getHeight()*0.8), true);