/// <summary>
/// Attempts to determine the <see cref="BitmapRotation"/> needed to fix the orientation of the given
/// <paramref name="imageFile"/>.
/// </summary>
public async Task <BitmapRotation> TryGetRecommendedRotationAsync(StorageFile imageFile, ImageScannerFormat format)
{
try
{
if (OcrEngine != null)
{
// get separate stream
using (IRandomAccessStream sourceStream = await imageFile.OpenAsync(FileAccessMode.Read))
{
BitmapDecoder decoder = await BitmapDecoder.CreateAsync(sourceStream);
Tuple <BitmapRotation, int> bestRotation;
// create rotated 0°
SoftwareBitmap bitmap = await decoder.GetSoftwareBitmapAsync();
OcrResult ocrResult = await OcrEngine.RecognizeAsync(bitmap);
bestRotation = new Tuple <BitmapRotation, int>(BitmapRotation.None, ocrResult.Text.Length);
using (InMemoryRandomAccessStream targetStream = new InMemoryRandomAccessStream())
{
// create rotated 90°
BitmapEncoder encoder = await HelperService.CreateOptimizedBitmapEncoderAsync(format, targetStream);
encoder.SetSoftwareBitmap(bitmap);
encoder.BitmapTransform.Rotation = BitmapRotation.Clockwise90Degrees;
await encoder.FlushAsync();
decoder = await BitmapDecoder.CreateAsync(targetStream);
bitmap = await decoder.GetSoftwareBitmapAsync();
ocrResult = await OcrEngine.RecognizeAsync(bitmap);
if (ocrResult.Text.Length > bestRotation.Item2)
{
bestRotation = new Tuple <BitmapRotation, int>(BitmapRotation.Clockwise90Degrees, ocrResult.Text.Length);
}
}
using (InMemoryRandomAccessStream targetStream = new InMemoryRandomAccessStream())
{
// create rotated 180°
BitmapEncoder encoder = await HelperService.CreateOptimizedBitmapEncoderAsync(format, targetStream);
encoder.SetSoftwareBitmap(bitmap);
encoder.BitmapTransform.Rotation = BitmapRotation.Clockwise90Degrees;
await encoder.FlushAsync();
decoder = await BitmapDecoder.CreateAsync(targetStream);
bitmap = await decoder.GetSoftwareBitmapAsync();
ocrResult = await OcrEngine.RecognizeAsync(bitmap);
if (ocrResult.Text.Length > bestRotation.Item2)
{
bestRotation = new Tuple <BitmapRotation, int>(BitmapRotation.Clockwise180Degrees, ocrResult.Text.Length);
}
}
using (InMemoryRandomAccessStream targetStream = new InMemoryRandomAccessStream())
{
// create rotated 270°
BitmapEncoder encoder = await HelperService.CreateOptimizedBitmapEncoderAsync(format, targetStream);
encoder.SetSoftwareBitmap(bitmap);
encoder.BitmapTransform.Rotation = BitmapRotation.Clockwise90Degrees;
await encoder.FlushAsync();
decoder = await BitmapDecoder.CreateAsync(targetStream);
bitmap = await decoder.GetSoftwareBitmapAsync();
ocrResult = await OcrEngine.RecognizeAsync(bitmap);
if (ocrResult.Text.Length > bestRotation.Item2)
{
bestRotation = new Tuple <BitmapRotation, int>(BitmapRotation.Clockwise270Degrees, ocrResult.Text.Length);
}
}
bitmap.Dispose();
if (bestRotation.Item2 < MinimumNumberOfWords)
{
// very low confidence, could just be random patterns
return(BitmapRotation.None);
}
else
{
return(bestRotation.Item1);
}
}
}
else
{
return(BitmapRotation.None);
}
}
catch (Exception exc)
{
LogService?.Log.Error(exc, "Determining the recommended rotation failed.");
AppCenterService?.TrackError(exc);
return(BitmapRotation.None);
}
}