android - BitmapFactory.decodeStream 内存不足，尽管使用了减少的样本大小

Question

我看了很多关于解码位图的内存分配问题的相关帖子，但使用官网提供的代码仍然无法找到以下问题的解决方案。

这是我的代码:

public static Bitmap decodeSampledBitmapFromResource(InputStream inputStream, int reqWidth, int reqHeight) {

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int len;
    try {
        while ((len = inputStream.read(buffer)) > -1) {
        baos.write(buffer, 0, len);
        }
        baos.flush();
        InputStream is1 = new ByteArrayInputStream(baos.toByteArray());
        InputStream is2 = new ByteArrayInputStream(baos.toByteArray());

        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(is1, null, options);

        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
        options.inPurgeable = true;
        options.inInputShareable = true;
        options.inJustDecodeBounds = false;
        options.inPreferredConfig = Bitmap.Config.ARGB_8888;
        return BitmapFactory.decodeStream(is2, null, options);

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

        return null;
    }
}

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {

        // Calculate ratios of height and width to requested height and width
        final int heightRatio = Math.round((float) height / (float) reqHeight);
        final int widthRatio = Math.round((float) width / (float) reqWidth);

        // Choose the smallest ratio as inSampleSize value, this will guarantee
        // a final image with both dimensions larger than or equal to the
        // requested height and width.
        inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
    }


    return inSampleSize;
}

bitmap = decodeSampledBitmapFromResource(inputStream, 600, 600); 

我在这一行中收到“3250016 字节分配内存不足错误”:

return BitmapFactory.decodeStream(is2, null, options);

在我看来，3.2 MB 足够小，可以分配。我哪里错了？我该如何解决这个问题？

编辑

查看此解决方案后 HERE由 N-Joy 提供，它适用于所需尺寸 300，但我需要的尺寸是 800，所以我仍然遇到错误。

Answer 1

decodeSampledBitmapFromResource 方法内存效率不高，因为它使用 3 个流:ByteArrayOutputStream baos、ByteArrayInputStream is1 和 ByteArrayInputStream is2，它们中的每一个都存储相同的流图像的数据(每个字节数组)。

当我用我的设备 (LG nexus 4) 测试将 SD 卡上的 2560x1600 图像解码为目标尺寸 800 时，它需要这样的东西:

03-13 15:47:52.557: E/DecodeBitmap(11177): dalvikPss (beginning) = 1780
03-13 15:47:53.157: E/DecodeBitmap(11177): dalvikPss (decoding) = 26393
03-13 15:47:53.548: E/DecodeBitmap(11177): dalvikPss (after all) = 30401 time = 999

我们可以看到:为解码 4096000 个像素图像分配了太多内存 (28.5 MB)。

解决方案:我们读取 InputStream 并将数据直接存储到一个字节数组中，并使用这个字节数组进行其余工作。
示例代码:

public Bitmap decodeSampledBitmapFromResourceMemOpt(
            InputStream inputStream, int reqWidth, int reqHeight) {

        byte[] byteArr = new byte[0];
        byte[] buffer = new byte[1024];
        int len;
        int count = 0;

        try {
            while ((len = inputStream.read(buffer)) > -1) {
                if (len != 0) {
                    if (count + len > byteArr.length) {
                        byte[] newbuf = new byte[(count + len) * 2];
                        System.arraycopy(byteArr, 0, newbuf, 0, count);
                        byteArr = newbuf;
                    }

                    System.arraycopy(buffer, 0, byteArr, count, len);
                    count += len;
                }
            }

            final BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            BitmapFactory.decodeByteArray(byteArr, 0, count, options);

            options.inSampleSize = calculateInSampleSize(options, reqWidth,
                    reqHeight);
            options.inPurgeable = true;
            options.inInputShareable = true;
            options.inJustDecodeBounds = false;
            options.inPreferredConfig = Bitmap.Config.ARGB_8888;

            int[] pids = { android.os.Process.myPid() };
            MemoryInfo myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
            Log.e(TAG, "dalvikPss (decoding) = " + myMemInfo.dalvikPss);

            return BitmapFactory.decodeByteArray(byteArr, 0, count, options);

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

            return null;
        }
    }

进行计算的方法:

public void onButtonClicked(View v) {
        int[] pids = { android.os.Process.myPid() };
        MemoryInfo myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
        Log.e(TAG, "dalvikPss (beginning) = " + myMemInfo.dalvikPss);

        long startTime = System.currentTimeMillis();

        FileInputStream inputStream;
        String filePath = Environment.getExternalStorageDirectory()
                .getAbsolutePath() + "/test2.png";
        File file = new File(filePath);
        try {
            inputStream = new FileInputStream(file);
//          mBitmap = decodeSampledBitmapFromResource(inputStream, 800, 800);
            mBitmap = decodeSampledBitmapFromResourceMemOpt(inputStream, 800,
                    800);
            ImageView imageView = (ImageView) findViewById(R.id.image);
            imageView.setImageBitmap(mBitmap);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        myMemInfo = mAM.getProcessMemoryInfo(pids)[0];
        Log.e(TAG, "dalvikPss (after all) = " + myMemInfo.dalvikPss
                + " time = " + (System.currentTimeMillis() - startTime));
    }

结果:

03-13 16:02:20.373: E/DecodeBitmap(13663): dalvikPss (beginning) = 1823
03-13 16:02:20.923: E/DecodeBitmap(13663): dalvikPss (decoding) = 18414
03-13 16:02:21.294: E/DecodeBitmap(13663): dalvikPss (after all) = 18414 time = 917