更改 android 中位图的大小以避免 OOM

Question

我一直在努力更改从我的服务器下载的位图的大小，因为我知道这是我遇到的 OOM 错误的问题。我已经尝试了其他示例和这个示例 https://developer.android.com/training/displaying-bitmaps/load-bitmap.html 但我无法确定如何使用它以及在何处使用它。我想将我的位图缩小到屏幕分辨率，但无法拼接起来。感谢您对此的任何帮助。

也不是说这是在 AsyncTask 中完成的，如果这会有所作为的话。

这是我设置位图的代码：

public class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {

BitmapFactory.Options options = new BitmapFactory.Options();

private final WeakReference<ImageView> imageViewReference;
Resources resources;

public ImageDownloaderTask(ImageView imageView) {
    imageViewReference = new WeakReference<ImageView>(imageView);
}


@Override
protected Bitmap doInBackground(String... params)
{
    return downloadBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
    if (isCancelled()) {
        bitmap = null;
        Log.d("HTTPS No go", bitmap.toString());
    }

    if (imageViewReference != null) {
        ImageView imageView = imageViewReference.get();
        if (imageView != null) {
            if (bitmap != null) {
                //Scale the bitmap to a smaller size
                imageView.setImageBitmap(bitmap);
            } else {
                Log.d("Downloading the image: ", "No Image found");
            }
        }

    }
}

//URL connection to download the image
private Bitmap downloadBitmap(String url) {

    HttpURLConnection urlConnection = null;
            try{
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            urlConnection.setRequestMethod("GET");
            int statusCode = urlConnection.getResponseCode();
            //check if the HTTP status code is equal to 200, which means that it is ok
            if (statusCode != 200) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                /*
                options.inJustDecodeBounds = true;
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, options);
                int imageHeight = options.outHeight;
                int imageWidth = options.outWidth;
                String imageType = options.outMimeType;
                int sampleSize = calculateInSampleSize(options, imageWidth, imageHeight);
                */
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                return bitmap;
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException 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) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) >= reqHeight
                && (halfWidth / inSampleSize) >= reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}

}

更新：

这稍微修复了它。它允许我只注销一次，但是当我第二次注销时，它会因旧的 OOM 错误而崩溃。

InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                BitmapFactory.Options options = new BitmapFactory.Options();
                options.inSampleSize=1; //try to decrease decoded image

                Bitmap bitmap = BitmapFactory.decodeStream(inputStream , null, options);
                return bitmap;
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } {}

Answer 1

我使用了这个代码：

    Bitmap outBitmap;

    // Decode image size
    BitmapFactory.Options o = new BitmapFactory.Options();
    o.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(photoPath, o);

    // The new size we want to scale to ensure memory usage is optimal
    int targetWidth;
    int targetHeight;
    if (o.outHeight > o.outWidth) {
        targetWidth = getResources().getInteger(R.integer.pic_width_px);
        targetHeight = getResources().getInteger(R.integer.pic_height_px);
    } else if (o.outHeight == o.outWidth) {
        targetWidth = targetHeight = getResources().getInteger(R.integer.pic_width_px);
    } else {
        targetWidth = getResources().getInteger(R.integer.pic_width_px);
        targetHeight = getResources().getInteger(R.integer.pic_height_px);
    }

    if (o.outWidth <= targetWidth && o.outHeight <= targetHeight) {
        // Return image as is without any additional scaling
        Bitmap origBitmap = BitmapFactory.decodeFile(photoPath, null);
        outBitmap = Bitmap.createBitmap(origBitmap, 0, 0, o.outWidth, o.outHeight, m, true);
        origBitmap.recycle();

        return outBitmap;
    }

    // Find the correct scale value. It should be the power of 2.
    int scale = 1;
    while(o.outWidth / scale / 2 >= targetWidth &&
            o.outHeight / scale / 2 >= targetHeight) {
        scale *= 2;
    }

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

    Bitmap scaledBitmap = BitmapFactory.decodeFile(photoPath, scaleOptions);
    return Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), m, true);

Answer 2

我认为您需要在将图像读入内存之前更改图像大小。

private Bitmap downloadBitmap(String url) {

    HttpURLConnection urlConnection = null;
            try{
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            urlConnection.setRequestMethod("GET");
            int statusCode = urlConnection.getResponseCode();
            //check if the HTTP status code is equal to 200, which means that it is ok
            if (statusCode != 200) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                //scale down the image and load
                options.inJustDecodeBounds = true;
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, options);
                options.inSampleSize = calculateInSampleSize(options, 100, 100);
                options.inJustDecodeBounds = false;
                return BitmapFactory.decodeStream(inputStream, null, options);   //I'm not sure here, because the inputStream used twice.
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } {}

    return null;
}

Answer 3

感谢所有提供帮助的人。我发现我的问题不是下载位图的大小，因为每次将它们添加到我的回收视图时，我都会自动调整它们的大小。这是由我在登录页面上播放的 gif 引起的，它只占用了那么多内存，一旦任何其他东西占用了内存，它就会杀死设备。

非常感谢这里的每一个人，谢谢你们。我自己认为问题出在图像下载上，因为这是通常的罪魁祸首。

Answer 4

几天前我遇到了同样的问题。理论上有两种方法可以做到这一点。要么你完全下载图像然后调整图像大小，要么你必须让你的服务器而不是应用程序来做这件事。我更喜欢第二种解决方案，我在其中发送所需的宽度、高度和所需的图像。服务器计算可能的比例，然后缩小尺寸并 returns 返回，打印图像。之后我只使用 HttpURLConnection 下载位图并从我的连接的输入流创建位图没有任何问题。

你的错误呢，也许你正在尝试先从流中计算然后创建它。当然它会导致崩溃，因为你正在尝试第二次读取输入流。在读取图像的元数据以了解尺寸时，您的光标已经移动到流中。现在当它尝试创建位图时失败了，因为它不是从流的第 0 个字节开始的。但是在中间的某个地方，你的光标上次停止的地方。因此，如果需要读取流两次，则需要先将输入流复制到某处才能读取流两次。希望对你有帮助。

更改 android 中位图的大小以避免 OOM

Change the size of a bitmap in android to avoid OOM

java

android

bitmap

scale

bitmapfactory