/// <summary>
/// extract text in the pdf page
/// </summary>
void ExtractText()
{
_charCode = -1;
_pageMatrix = PdfPage.GetDefaultMatrix();
_pageHeight = PdfPage.GetPageHeight();
_textLines = new PdfLineOfText[((int)_pageHeight >> 2) + 8];
using (ElementReader page_reader = new ElementReader())
{
page_reader.Begin(PdfPage);
ProcessElements(page_reader);
}
PdfLineOfText preLt = null;
for (int i = 0; i < _textLines.Length; i++)
{
var lt = _textLines[i];
if (preLt != null && lt != null && preLt.FirstChar.Top - lt.FirstChar.Top < 3)
{
preLt.AddPdfChars(lt.Chars);
_textLines[i] = lt = null;
}
preLt = lt;
}
}
// prcoess text element
void ProcessTextElement(Element element)
{
double x, y;
var text = element.GetTextString();
if (text.Trim().Length == 0)
{
return;
}
var matrix = element.GetCTM();
matrix.Concat(_pageMatrix.m_a, _pageMatrix.m_b, _pageMatrix.m_c, _pageMatrix.m_d, _pageMatrix.m_h, _pageMatrix.m_v);
matrix *= element.GetTextMatrix();
var gs = element.GetGState();
var font = gs.GetFont();
double font_size = Math.Abs(gs.GetFontSize() * Math.Sqrt(matrix.m_b * matrix.m_b + matrix.m_d * matrix.m_d));// font_size * font_sz_scale_factor;
// remove watermark
if (font_size > 32 && gs.GetTextRenderMode() == GState.TextRenderingMode.e_stroke_text)
{
return;
}
int index = -1;
var chs = new PdfChar[text.Length];
for (CharIterator itr = element.GetCharIterator(); itr.HasNext(); itr.Next())
{
index++;
x = itr.Current().x;
y = itr.Current().y;
matrix.Mult(ref x, ref y);
var ch = text[index];
if (ch == 65533)
{
//in some pdf files,we can't find the right unicode for some characters by using pdftron,
//so we record a pdf charcode with a right unicode value,and then computing the unicode for those bad characters.
if (_charCode > 0)
{
ch = (char)(_charUnicode + itr.Current().char_code - _charCode);
}
}
else if (ch >= 0x4e00)
{
_charUnicode = ch;
_charCode = itr.Current().char_code;
}
chs[index] = new PdfChar(ch, new System.Windows.Rect(x, y, font.GetWidth(itr.Current().char_code) * 0.001 * font_size, font_size));
}
var pchar = chs[0];
var dis = _pageHeight - pchar.Top;
index = (int)dis >> 2;
var textLine = _textLines[index];
if (textLine == null)
{
_textLines[index] = textLine = new PdfLineOfText();
}
textLine.AddPdfChars(chs);
}
