如果你用的是Fresco，你可以用这个

final ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(uri)
.setRotationOptions(RotationOptions.autoRotate())
.build();

mSimpleDraweeView.setController(
Fresco.newDraweeControllerBuilder()
    .setImageRequest(imageRequest)
    .build());

这将根据Exif数据自动旋转图像。

来源:https://frescolib.org/docs/rotation.html

这是Xamarin。Android版本:

来自@Jason Robinson的回答:

Bitmap rotate(Bitmap bitmap, int angle)
{
    var matrix = new Matrix();
    matrix.PostRotate(angle);

    return Bitmap.CreateBitmap(bitmap, 0, 0, bitmap.Width, bitmap.Height, matrix, true);
}

Bitmap rotateIfRequired(Bitmap bitmap, string imagePath)
{
    var ei = new ExifInterface(imagePath);
    var orientation = ei.GetAttributeInt(ExifInterface.TagOrientation, (int)Android.Media.Orientation.Undefined);

    switch (orientation)
    {
        case (int)Android.Media.Orientation.Rotate90: return rotate(bitmap, 90);
        case (int)Android.Media.Orientation.Rotate180: return rotate(bitmap, 180);
        case (int)Android.Media.Orientation.Rotate270: return rotate(bitmap, 270);
        default: return bitmap;
    }
}

然后calculateInSampleSize方法:

int calculateInSampleSize(BitmapFactory.Options options, int reqW, int reqH)
{
    float h = options.OutHeight;
    float w = options.OutWidth;
    var inSampleSize = 1;

    if (h > reqH || w > reqW)
    {
        if (reqH == 0) inSampleSize = (int)Math.Floor(w / reqW);
        else if (reqW == 0) inSampleSize = (int)Math.Floor(h / reqH);
        else
        {
            var hRatio = (int)Math.Floor(h / reqH);
            var wRatio = (int)Math.Floor(w / reqW);
            inSampleSize = false ? Math.Max(hRatio, wRatio) : Math.Min(hRatio, wRatio);
        }
    }

    return inSampleSize;
}

来自@Sami Eltamawy的回答:

Bitmap handleSamplingAndRotationBitmap(string imagePath)
{
    var maxHeight = 1024;
    var maxWidth = 1024;

    var options = new BitmapFactory.Options();
    options.InJustDecodeBounds = true;
    BitmapFactory.DecodeFile(imagePath, options);

    options.InSampleSize = calculateInSampleSize(options, maxWidth, maxHeight);

    options.InJustDecodeBounds = false;

    var bitmap = BitmapFactory.DecodeFile(imagePath, options);

    bitmap = rotateIfRequired(bitmap, imagePath);

    return bitmap;
}

可悲的是，上面的@jason-robinson回答对我没用。

虽然旋转函数工作得很完美:

public static Bitmap rotateImage(Bitmap source, float angle) {
    Matrix matrix = new Matrix();
    matrix.postRotate(angle);
    return Bitmap.createBitmap(source, 0, 0, source.getWidth(), source.getHeight(), matrix,
            true);
}

我必须做以下事情来获得方向，因为Exif方向总是0

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode,resultCode,data);
    if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && data != null) {
            Uri selectedImage = data.getData();
            String[] orientationColumn = {MediaStore.Images.Media.ORIENTATION};
            Cursor cur = managedQuery(imageUri, orientationColumn, null, null, null);
            int orientation = -1;
            if (cur != null && cur.moveToFirst()) {
                    orientation = cur.getInt(cur.getColumnIndex(orientationColumn[0]));
            }
            InputStream imageStream = getContentResolver().openInputStream(selectedImage);
            Bitmap bitmap = BitmapFactory.decodeStream(imageStream);
            switch(orientation) {
                    case 90:
                            bitmap = rotateImage(chosen_image_bitmap, 90);
                            break;
                    case 180:
                            bitmap = rotateImage(chosen_image_bitmap, 180);
                            break;
                    case 270:
                            bitmap = rotateImage(chosen_image_bitmap, 270);
                            break;
                    default:
                            break;
            }
            imageView.setImageBitmap(bitmap );

使用Glide库对我很有用。旋转是自动的。

Bitmap bitmap = Glide.with(myContext).asBitmap().load(imageFilePath).submit(SIZE_ORIGINAL, SIZE_ORIGINAL).get();

然后将该位图保存为JPEG格式的文件。

如果你只是想加载到一个ImageView而不是保存到一个文件:

Glide.with(myContext).load(imageFilePath).into(myImageView)

如果有人在Android 4.4 (KitKat)上使用ExifInterface获得方向时遇到问题，这可能是因为从URI获得了错误的路径。在堆栈溢出问题中看到一个解决方案，从URI获得真正的路径，Android奇巧新的存储访问框架

一句话解决方案:

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

Or

Picasso.with(context).load("file:" + photoPath).into(imageView);

这将自动检测旋转和放置图像在正确的方向

Picasso是一个非常强大的库，用于处理应用中的图像，包括: 复杂的图像转换与最小的内存使用。