我有一个应用程序，为用户显示相当多的图片，我们已经看到了很多的错误报告与的OutOfMemoryError 例外。

I have an app that displays quite a few images for the user, and we've been seeing a lot of error reports with OutOfMemoryError exception.

我们现在做的是这样的：

What we currently do is this:

// Check if image is a landscape image
if (bmp.getWidth() > bmp.getHeight()) {
    // Rotate it to show as a landscape
    Matrix m = image.getImageMatrix();
    m.postRotate(90);
    bmp = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), m, true);
}
image.setImageBitmap(bmp);

与此明显的问题是，我们必须重新从存储器中的图像的位图和旋转矩阵，这对于内存相当昂贵的。

The obvious problem with this is that we have to recreate the bitmap from the image on memory and rotate the matrix, this is quite expensive for the memory.

我的问题很简单：

有没有更好的办法，而不会造成旋转图像的OutOfMemoryError ？

Is there a better way to rotate images without causing OutOfMemoryError?

推荐答案

旋转大图像的2种方法：

2 methods of rotating a large image:

使用JNI，如对这个职位。

使用一个文件：这是一个非常缓慢的方式（取决于输入和设备，但仍然很慢），这使代替把球送入德$ C $光盘旋转图像插入到磁盘第一，内存。

using a file : it's a very slow way (depending on the input and the device , but still very slow) , which puts the decoded rotated image into the disk first , instead of putting it into the memory .

$ C $使用文件c是如下：

code of using a file is below:

private void rotateCw90Degrees()
  {
  Bitmap bitmap=BitmapFactory.decodeResource(getResources(),INPUT_IMAGE_RES_ID);
  // 12 => 7531
  // 34 => 8642
  // 56 =>
  // 78 =>
  final int height=bitmap.getHeight();
  final int width=bitmap.getWidth();
  try
    {
    final DataOutputStream outputStream=new DataOutputStream(new BufferedOutputStream(openFileOutput(ROTATED_IMAGE_FILENAME,Context.MODE_PRIVATE)));
    for(int x=0;x<width;++x)
      for(int y=height-1;y>=0;--y)
        {
        final int pixel=bitmap.getPixel(x,y);
        outputStream.writeInt(pixel);
        }
    outputStream.flush();
    outputStream.close();
    bitmap.recycle();
    final int newWidth=height;
    final int newHeight=width;
    bitmap=Bitmap.createBitmap(newWidth,newHeight,bitmap.getConfig());
    final DataInputStream inputStream=new DataInputStream(new BufferedInputStream(openFileInput(ROTATED_IMAGE_FILENAME)));
    for(int y=0;y<newHeight;++y)
      for(int x=0;x<newWidth;++x)
        {
        final int pixel=inputStream.readInt();
        bitmap.setPixel(x,y,pixel);
        }
    inputStream.close();
    new File(getFilesDir(),ROTATED_IMAGE_FILENAME).delete();
    saveBitmapToFile(bitmap); //for checking the output
    }
  catch(final IOException e)
    {
    e.printStackTrace();
    }
  }