public double GetSkewAngle(Bitmap image)
{
var bitArrays = UnsafeImageOps.ConvertToBitArrays(image);
var h = image.Height;
var w = image.Width;
// Ignore a bit of the top/bottom so that artifacts from the edge
// of the scan area aren't counted. (Left/right don't matter since
// we only look at near-horizontal lines.)
var yOffset = (int)Math.Round(h * IGNORE_EDGE_FRACTION);
var sinCos = PrecalculateSinCos();
// TODO: Consider reducing the precision of distance or angle,
// TODO: possibly with a second pass to restore precision.
var dCount = 2 * (w + h);
var scores = new int[dCount, ANGLE_STEPS];
// TODO: This should be a good candidate for OpenCL optimization.
// TODO: If you parallelize over the angle, you're operating over
// TODO: the same input data with the same branches.
for (var y = 1 + yOffset; y <= h - 2 - yOffset; y++)
{
for (var x = 1; x <= w - 2; x++)
{
if (!bitArrays[y][x] || bitArrays[y + 1][x])
{
continue;
}
for (var i = 0; i < ANGLE_STEPS; i++)
{
var sc = sinCos[i];
var d = (int)(y * sc.cos - x * sc.sin + w);
scores[d, i]++;
}
}
}
var angles = GetAnglesOfBestLines(scores, dCount);
var cluster = ClusterAngles(angles);
if (cluster.Length < angles.Length / 2)
{
// Could not find a consistent skew angle
return(0);
}
return(cluster.Sum() / cluster.Length);
}
private async Task <(ScannedImage, bool)> Transfer(Lazy <KeyValueScanOptions> options, int pageNumber)
{
return(await Task.Factory.StartNew(() =>
{
Stream stream;
if (ScanParams.NoUi)
{
stream = saneWrapper.ScanOne(ScanDevice.Id, options.Value, null, CancelToken);
}
else
{
var form = formFactory.Create <FScanProgress>();
var unifiedCancelToken = CancellationTokenSource.CreateLinkedTokenSource(form.CancelToken, CancelToken).Token;
form.Transfer = () => saneWrapper.ScanOne(ScanDevice.Id, options.Value, form.OnProgress, unifiedCancelToken);
form.PageNumber = pageNumber;
((FormBase)Application.OpenForms[0]).SafeInvoke(() => form.ShowDialog());
if (form.Exception != null)
{
form.Exception.PreserveStackTrace();
throw form.Exception;
}
if (form.DialogResult == DialogResult.Cancel)
{
return (null, true);
}
stream = form.ImageStream;
}
if (stream == null)
{
return (null, true);
}
using (stream)
using (var output = Image.FromStream(stream))
using (var result = scannedImageHelper.PostProcessStep1(output, ScanProfile, false))
{
if (blankDetector.ExcludePage(result, ScanProfile))
{
return (null, false);
}
// By converting to 1bpp here we avoid the Win32 call in the BitmapHelper conversion
// This converter also has the side effect of working even if the scanner doesn't support Lineart
using (var encoded = ScanProfile.BitDepth == ScanBitDepth.BlackWhite ? UnsafeImageOps.ConvertTo1Bpp(result, -ScanProfile.Brightness) : result)
{
var image = new ScannedImage(encoded, ScanProfile.BitDepth, ScanProfile.MaxQuality, ScanProfile.Quality);
scannedImageHelper.PostProcessStep2(image, result, ScanProfile, ScanParams, 1, false);
var tempPath = scannedImageHelper.SaveForBackgroundOcr(result, ScanParams);
scannedImageHelper.RunBackgroundOcr(image, ScanParams, tempPath);
return (image, false);
}
}
}, TaskCreationOptions.LongRunning));
}