How to know if text exceeds the fill box in itextSharp

问题

I am using the following code:

PdfReader PDFReader = new PdfReader("c:\\file.pdf");

FileStream Stream = new FileStream("c:\\new.pdf", FileMode.Create, FileAccess.Write);

PdfStamper PDFStamper = new PdfStamper(PDFReader, Stream);

for (int iCount = 0; iCount < PDFStamper.Reader.NumberOfPages; iCount++)
{
    iTextSharp.text.Rectangle PageSize = PDFReader.GetCropBox(iCount + 1);
    PdfContentByte PDFData = PDFStamper.GetOverContent(iCount + 1);
    BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);
    PDFData.BeginText();
    PDFData.SetColorFill(CMYKColor.RED);
    PDFData.SetFontAndSize(baseFont, 20);
    PDFData.ShowTextAligned(PdfContentByte.ALIGN, SAMPLE DOCUMENT", (PageSize.Right + PageSize.Left) / 2, (PageSize.Top + PageSize.Bottom) / 2, 45);
    PDFData.EndText();
}

PDFStamper.Close();
PDFReader.Close();

But sometimes the overlaid text exceeds the page size because I have hard coded the font as 20. So, is there any way to know if the overlaid text will exceed the page size? Because I want to use code like I will then use:

if(pagesize exceeds)
  reduce font size by 1 point and check again .....

If the above doesn't work, then my next step is to use a PNG image that has the overlaid text in it and its background as transparent. then resize the image according to the pagesize and then overlay it.

however, I will prefer the first part. if not, then I will go for the second option.

回答1:

After doing some minor calculations, this method should calculate the maximum font size to use for such a vertical text and apply it:

void Stamp(PdfContentByte cb, Rectangle rect, BaseFont bf, string text)
{
    int altitude = Math.Max(bf.GetAscent(text), bf.GetDescent(text));
    int width = bf.GetWidth(text);
    double horizontalFit = Math.Sqrt(2.0) * 1000 * (rect.Left + rect.Right) / (width + 2 * altitude);
    double verticalFit = Math.Sqrt(2.0) * 1000 * (rect.Bottom + rect.Top) / (width + 2 * altitude);
    double fit = Math.Min(horizontalFit, verticalFit);

    cb.BeginText();
    cb.SetColorFill(CMYKColor.RED);
    cb.SetFontAndSize(bf, (float) fit);
    cb.ShowTextAligned(PdfContentByte.ALIGN_CENTER, text, (rect.Right + rect.Left) / 2, (rect.Top + rect.Bottom) / 2, 45);
    cb.EndText();
}

You can call it like this:

using (PdfReader reader = new PdfReader(source))
using (PdfStamper stamper = new PdfStamper(reader, new FileStream(dest, FileMode.Create, FileAccess.Write)))
{
    for (int iCount = 0; iCount < reader.NumberOfPages; iCount++)
    {
        Rectangle PageSize = reader.GetCropBox(iCount + 1);
        PdfContentByte PDFData = stamper.GetOverContent(iCount + 1);
        BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);
        Stamp(PDFData, PageSize, baseFont, "SAMPLE DOCUMENT");
    }
}

(By the way, I used your BaseFont but you should be aware that iText(Sharp) will ignore BaseFont.EMBEDDED for standard 14 fonts like BaseFont.HELVETICA.)

The result looks like this:

PS: If you (as expressed in your question) really don't want to use a font size above 20, you have to Min the fit value again with 20.

来源：https://stackoverflow.com/questions/34470511/how-to-know-if-text-exceeds-the-fill-box-in-itextsharp

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