如何判断 PDF 文本是否已旋转

Question

I'm trying to pull text from a PDF using iText7. I'm using the IEventListener to get all the parts of the page, though some of the text is rotated. I can find examples for how to insert rotated text into a PDF, but can't find anything about how I can tell if a given text segment is rotated.

Can anyone help?

public void EventOccurred(IEventData data, EventType type)
{
    PdfPart part = null;

    switch (type)
    {
        case EventType.BEGIN_TEXT:
            break;
        case EventType.RENDER_TEXT:
            part = new PdfTextPart(PageNumber, data as TextRenderInfo);
            Parts.Add(part);
            break;
        case EventType.END_TEXT:
            break;
        case EventType.RENDER_IMAGE:
            var imageData = data as ImageRenderInfo;
            //this.HandleImage(imageData);
            break;
        case EventType.RENDER_PATH:
            part = new PdfLinePart(PageNumber, data as PathRenderInfo);
            Parts.Add(part);
            break;
        case EventType.CLIP_PATH_CHANGED:
            break;
        default:
            break;
    }
}

public PdfTextPart(Int32 pageNumber, TextRenderInfo info) : base(pageNumber)
{
    Text = info.GetText();

    var font = info.GetFont().GetFontProgram().GetFontNames();
    Font = font.GetFontName();

    if (font.IsItalic()) { this.IsItalic = true; }
    if (font.IsBold()) { this.IsBold = true; }
    if (font.IsUnderline()) { this.IsUnderline = true; }
}

Answer 1

TextRenderInfo has a base line. This base line is a LineSegment and as such has a start point and an end point. Now you merely have to determine the angle of the line between those two points.

Ie for a TextRenderInfo info :

LineSegment baseline = info.GetBaseline();
Vector startPoint = baseline.GetStartPoint();
Vector endPoint = baseline.GetEndPoint();
Vector direction = endLocation.Subtract(startLocation);
double angle = Math.Atan2(direction.Get(Vector.I2), direction.Get(Vector.I1));

The result obviously is in radian measure.

You may additionally have to take into account the page rotation which (if I recall correctly) is not calculated into the coordinates above.