private PdfRectangle GetBoundingBoxOther(IReadOnlyList <TextLine> lines)
{
var points = lines.SelectMany(l => new[]
{
l.BoundingBox.BottomLeft,
l.BoundingBox.BottomRight,
l.BoundingBox.TopLeft,
l.BoundingBox.TopRight
});
// Candidates bounding boxes
var obb = Geometry.GeometryExtensions.MinimumAreaRectangle(points);
var obb1 = new PdfRectangle(obb.BottomLeft, obb.TopLeft, obb.BottomRight, obb.TopRight);
var obb2 = new PdfRectangle(obb.BottomRight, obb.BottomLeft, obb.TopRight, obb.TopLeft);
var obb3 = new PdfRectangle(obb.TopRight, obb.BottomRight, obb.TopLeft, obb.BottomLeft);
// Find the orientation of the OBB, using the baseline angle
// Assumes line order is correct
var lastLine = lines[lines.Count - 1];
var baseLineAngle = Distances.BoundAngle180(Distances.Angle(lastLine.BoundingBox.BottomLeft, lastLine.BoundingBox.BottomRight));
double deltaAngle = Math.Abs(Distances.BoundAngle180(obb.Rotation - baseLineAngle));
double deltaAngle1 = Math.Abs(Distances.BoundAngle180(obb1.Rotation - baseLineAngle));
if (deltaAngle1 < deltaAngle)
{
deltaAngle = deltaAngle1;
obb = obb1;
}
double deltaAngle2 = Math.Abs(Distances.BoundAngle180(obb2.Rotation - baseLineAngle));
if (deltaAngle2 < deltaAngle)
{
deltaAngle = deltaAngle2;
obb = obb2;
}
double deltaAngle3 = Math.Abs(Distances.BoundAngle180(obb3.Rotation - baseLineAngle));
if (deltaAngle3 < deltaAngle)
{
obb = obb3;
}
return(obb);
}
private static PdfRectangle GetBoundingBoxOther(IReadOnlyList <Word> words)
{
var baseLinePoints = words.SelectMany(r => new[]
{
r.BoundingBox.BottomLeft,
r.BoundingBox.BottomRight,
}).ToList();
// Fitting a line through the base lines points
// to find the orientation (slope)
double x0 = baseLinePoints.Average(p => p.X);
double y0 = baseLinePoints.Average(p => p.Y);
double sumProduct = 0;
double sumDiffSquaredX = 0;
for (int i = 0; i < baseLinePoints.Count; i++)
{
var point = baseLinePoints[i];
var x_diff = point.X - x0;
var y_diff = point.Y - y0;
sumProduct += x_diff * y_diff;
sumDiffSquaredX += x_diff * x_diff;
}
double cos = 0;
double sin = 1;
if (sumDiffSquaredX > 1e-3)
{
// not a vertical line
double angleRad = Math.Atan(sumProduct / sumDiffSquaredX); // -π/2 ≤ θ ≤ π/2
cos = Math.Cos(angleRad);
sin = Math.Sin(angleRad);
}
// Rotate the points to build the axis-aligned bounding box (AABB)
var inverseRotation = new TransformationMatrix(
cos, -sin, 0,
sin, cos, 0,
0, 0, 1);
var transformedPoints = words.SelectMany(r => new[]
{
r.BoundingBox.BottomLeft,
r.BoundingBox.BottomRight,
r.BoundingBox.TopLeft,
r.BoundingBox.TopRight
}).Distinct().Select(p => inverseRotation.Transform(p));
var aabb = new PdfRectangle(transformedPoints.Min(p => p.X),
transformedPoints.Min(p => p.Y),
transformedPoints.Max(p => p.X),
transformedPoints.Max(p => p.Y));
// Rotate back the AABB to obtain to oriented bounding box (OBB)
var rotateBack = new TransformationMatrix(
cos, sin, 0,
-sin, cos, 0,
0, 0, 1);
// Candidates bounding boxes
var obb = rotateBack.Transform(aabb);
var obb1 = new PdfRectangle(obb.BottomLeft, obb.TopLeft, obb.BottomRight, obb.TopRight);
var obb2 = new PdfRectangle(obb.BottomRight, obb.BottomLeft, obb.TopRight, obb.TopLeft);
var obb3 = new PdfRectangle(obb.TopRight, obb.BottomRight, obb.TopLeft, obb.BottomLeft);
// Find the orientation of the OBB, using the baseline angle
// Assumes word order is correct
var firstWord = words[0];
var lastWord = words[words.Count - 1];
var baseLineAngle = Distances.Angle(firstWord.BoundingBox.BottomLeft, lastWord.BoundingBox.BottomRight);
double deltaAngle = Math.Abs(Distances.BoundAngle180(obb.Rotation - baseLineAngle));
double deltaAngle1 = Math.Abs(Distances.BoundAngle180(obb1.Rotation - baseLineAngle));
if (deltaAngle1 < deltaAngle)
{
deltaAngle = deltaAngle1;
obb = obb1;
}
double deltaAngle2 = Math.Abs(Distances.BoundAngle180(obb2.Rotation - baseLineAngle));
if (deltaAngle2 < deltaAngle)
{
deltaAngle = deltaAngle2;
obb = obb2;
}
double deltaAngle3 = Math.Abs(Distances.BoundAngle180(obb3.Rotation - baseLineAngle));
if (deltaAngle3 < deltaAngle)
{
obb = obb3;
}
return(obb);
}