/// <summary>
/// Auto rotates an image and returns the angle used to rotate the image
/// </summary>
/// <returns></returns>
public static double?AutoRotateImage(string inputFileFolderPath, string inputFileName, bool showMessageBoxes, ImageBox iboxRaw, ImageBox iboxProcessed, string outputFileFolderPath, string outputFileName, out double msecRotation)
{
double?rotationAngle = null;
msecRotation = 0;
try
{
rotationAngle = GetRotationAngle(inputFileFolderPath, inputFileName, showMessageBoxes, iboxRaw, iboxProcessed, out msecRotation);
if (rotationAngle != null)
{
Mat rotated = new Mat();
Mat src = new Mat(inputFileFolderPath + inputFileName, ImreadModes.Unchanged);
Cv2E.RotateDegrees(src, rotated, (double)rotationAngle);
rotated.SaveImage(outputFileFolderPath + outputFileName);
}
}
catch (Exception ex)
{
}
return(rotationAngle);
}
public static double?GetRotationAngle(string inputFileFolderPath, string inputFileName, bool showMessageBoxes, ImageBox iboxRaw, ImageBox iboxProcessed, out double msecElapsed)
{
double?rotationAngle = null;
msecElapsed = 0;
// Hough algo does a bad job detecting horizontal lines. So we rotate the image by a set amount before running the Hough.
double houghRotationOffsetAngle = 25.0;
try
{
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();
if (iboxProcessed != null)
{
iboxProcessed.Image = null;
iboxProcessed.Refresh();
}
Mat rotated = new Mat();
Mat src = new Mat(inputFileFolderPath + inputFileName, ImreadModes.Grayscale);
if (showMessageBoxes && iboxRaw != null)
{
iboxRaw.Image = OpenCvSharp.Extensions.BitmapConverter.ToBitmap(src);
}
// Not needed if we read as grayscale to start with.
//Mat src8UC1 = new Mat();
//src.ConvertTo(src8UC1, MatType.CV_8UC1);
// I'm not sure why we do the gauss - It seems like everyone does it, it's cheap, so we do it. ~Ed
Mat gauss = new Mat();
Cv2.GaussianBlur(src, gauss, new OpenCvSharp.Size(3, 3), 2, 2);
LogEvent("gauss", showMessageBoxes, gauss, iboxProcessed);
// An attempt to get the contrast across the image to be somewhat uniform.
CLAHE claheFilter = Cv2.CreateCLAHE(4, new OpenCvSharp.Size(10, 10));
Mat clahe = new Mat();
claheFilter.Apply(gauss, clahe);
LogEvent("clahe", showMessageBoxes, clahe, iboxProcessed);
// An attempt to get the contrast across the image to be somewhat uniform.
Mat hist = new Mat();
Cv2.EqualizeHist(gauss, hist);
LogEvent("hist", showMessageBoxes, hist, iboxProcessed);
// Grab a template from some middle part of the image. Eventually, the size and location of this
// template will be specified. It is very possible we'll have to grab multiple templates, as the
// location of the template may impact the accuracy of the rotation.
// e.g. - if the template is an image of a damaged device (which may happen at any location), the calculated
// rotation may be wrong. Testing is required.
// The locations where the template matches will create an image with lines that are offset from 0/90 degrees.
// This is because we can assume that the devices are orthogonal to one another, even if the image itself is
// offset rotationally.
Rect r1 = new Rect(new OpenCvSharp.Point(1000, 1000), new OpenCvSharp.Size(500, 300));
var roi = new Mat(clahe, r1);
Mat template = new Mat(new OpenCvSharp.Size(500, 300), MatType.CV_8UC1);
roi.CopyTo(template);
LogEvent("template", showMessageBoxes, template, iboxProcessed);
Mat templateMatch = new Mat();
Cv2.MatchTemplate(clahe, template, templateMatch, TemplateMatchModes.CCoeffNormed);
LogEvent("templatematch", showMessageBoxes, templateMatch, iboxProcessed);
Mat normalized = new Mat();
normalized = templateMatch.Normalize(0, 255, NormTypes.MinMax);
normalized.ConvertTo(normalized, MatType.CV_8UC1);
LogEvent("normalized template match", showMessageBoxes, normalized, iboxProcessed);
// This winnows down the number of matches.
Mat thresh = new Mat();
Cv2.Threshold(normalized, thresh, 200, 255, ThresholdTypes.Binary);
LogEvent("threshold template match", showMessageBoxes, thresh, iboxProcessed);
// rotate the image because hough doesn't work very well to find horizontal lines.
Mat rotatedThresh = new Mat();
Cv2E.RotateDegrees(thresh, rotatedThresh, houghRotationOffsetAngle);
LogEvent("rotatedThresh", showMessageBoxes, rotatedThresh, iboxProcessed);
Mat erode = new Mat();
Cv2.Erode(rotatedThresh, erode, new Mat());
LogEvent("erode", showMessageBoxes, erode, iboxProcessed);
LineSegmentPoint[] segHoughP = Cv2.HoughLinesP(rotatedThresh, 1, Math.PI / 1800, 2, 10, 600);
Mat imageOutP = new Mat(src.Size(), MatType.CV_8UC3);
// We're limiting the rotation correction to +/- 10 degrees. So we only care about hough lines that fall within 80 to 100 or 170 to 190
List <double> anglesNear90 = new List <double>();
List <double> anglesNear0 = new List <double>();
foreach (LineSegmentPoint s in segHoughP)
{
try
{
// Add lines to the image, if we're going to look at it.
if (showMessageBoxes)
{
imageOutP.Line(s.P1, s.P2, Scalar.White, 1, LineTypes.AntiAlias, 0);
}
var radian = Math.Atan2((s.P1.Y - s.P2.Y), (s.P1.X - s.P2.X));
var angle = ((radian * (180 / Math.PI) + 360) % 360);
// We rotated the image because the hough algo does a bad job with small horizontal lines. So we take that rotation back out here.
angle += houghRotationOffsetAngle;
angle -= 180;
if (angle > 80 && angle < 100)
{
anglesNear90.Add(angle);
if (showMessageBoxes)
{
imageOutP.Line(s.P1, s.P2, Scalar.Red, 1, LineTypes.AntiAlias, 0);
}
}
if (angle > -10 && angle < 10)
{
anglesNear0.Add(angle);
if (showMessageBoxes)
{
imageOutP.Line(s.P1, s.P2, Scalar.Orange, 1, LineTypes.AntiAlias, 0);
}
}
}
catch (Exception ex)
{
// there's always some infinity risk with atan, yes? Maybe. I don't want to fail on horizontal or vertical line edge cases.
}
}
double meanAngleNear0 = 0;
if (anglesNear0.Count > 0)
{
meanAngleNear0 = anglesNear0.Mean();
}
double meanAngleNear90 = 90;
if (anglesNear90.Count > 0)
{
meanAngleNear90 = anglesNear90.Mean();
}
// Use both the vertical and horizontal to calculate the image angle with a weighted average. It might be more accurate to use median instead of mean here.
rotationAngle = ((meanAngleNear0) * anglesNear0.Count + (meanAngleNear90 - 90) * anglesNear90.Count) / (anglesNear0.Count + anglesNear90.Count);
LogEvent("hough lines", showMessageBoxes, imageOutP, iboxProcessed);
stopWatch.Stop();
// Get the elapsed time as a TimeSpan value. Less than 400msec in debug mode via IDE.
TimeSpan ts = stopWatch.Elapsed;
msecElapsed = ts.TotalMilliseconds;
}
catch (Exception ex)
{
}
return(rotationAngle);
}
