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;
}

最好试着以特定的方向照相。

android:screenOrientation="landscape"
android:configChanges="orientation|keyboardHidden"

为了获得最好的结果，在cameraview活动中给出景观方向。

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

通过使用滑动库，你可以得到图像与精确的方向，而不需要检查旋转

在kotlin

CoroutineScope(Dispatchers.IO).launch {
         var bitmap = Glide.with(context).asBitmap().load(imagePathOrUriOrLink)
                /*.apply(
                    RequestOptions()
                        .override(MAXIMUM_IMAGE_RESOLUTION)
                )*/ //uncomment it if you want original image
                /*.diskCacheStrategy(DiskCacheStrategy.NONE).skipMemoryCache(true)*/ //uncomment it you want to not cache image
                .submit().get()//this is synchronous approach  
}

使用这个依赖

api 'com.github.bumptech.glide:glide:4.12.0'
kapt 'com.github.bumptech.glide:compiler:4.12.0'

我根据@Jason Robinson的回答创建了一个Kotlin扩展函数，简化了Kotlin开发人员的操作。我希望这能有所帮助。

fun Bitmap.fixRotation(uri: Uri): Bitmap? {

    val ei = ExifInterface(uri.path)

    val orientation: Int = ei.getAttributeInt(
        ExifInterface.TAG_ORIENTATION,
        ExifInterface.ORIENTATION_UNDEFINED
    )

    return when (orientation) {
        ExifInterface.ORIENTATION_ROTATE_90 -> rotateImage( 90f)
        ExifInterface.ORIENTATION_ROTATE_180 -> rotateImage( 180f)
        ExifInterface.ORIENTATION_ROTATE_270 -> rotateImage( 270f)
        ExifInterface.ORIENTATION_NORMAL -> this
        else -> this
    }
}

fun Bitmap.rotateImage(angle: Float): Bitmap? {
    val matrix = Matrix()
    matrix.postRotate(angle)
    return Bitmap.createBitmap(
        this, 0, 0, width, height,
        matrix, true
    )
}

你可以像文档中的谷歌那样读取摄像头传感器的方向:https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html

SENSOR_ORIENTATION

Added in API level 21
Key<Integer> SENSOR_ORIENTATION
Clockwise angle through which the output image needs to be rotated to be upright on the device screen in its native orientation.

Also defines the direction of rolling shutter readout, which is from top to bottom in the sensor's coordinate system.

Units: Degrees of clockwise rotation; always a multiple of 90

Range of valid values:
0, 90, 180, 270

This key is available on all devices.

示例代码:

CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
int orientation = 0;
try {
    String cameraId = manager.getCameraIdList()[0];
    CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
    orientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
}
catch (Exception e)
{
}