PDF files are display oriented and not content oriented. Usually the page content has no internal structure (it is just a bunch of drawing instructions), this is why it is so hard to extract structured content.
No matter what PDF library you choose you will have to write some code to process your PDF files. If you can post a sample file I can take a look at it and offer some suggestions.
UPDATE:
I looked at the file and the solution below shows a possible implementation using XFINIUM.PDF library (Disclaimer: I work for the company that develops XFINIUM.PDF).
As I said before the PDF file content has no structure, it is just a long list of drawing instructions (no matter it is showText or strokePath). This requires to extract the text content along with its position and perform the analysis of the text fragments based on their position, the analysis which will be specific to your files.
In your text the section separators are not images, the symbol is actually the letter 'f' printed with a symbol font so it is easy to detect when a section starts.
The text that follows is analysed based on its position and each text fragment is either added to current line (if Y baseline is roughly the same) or to a new line. A line of text consists of one or more text fragments, depending on how the PDF generator decides to draw it.
After the section content (a list of strings) has been retrieved, it is processed to detect the title. The first n lines that use only upper-case are considered to be the title.
The code below shows how to implement this logic, but it is just the basics to get you started.
The Section class:
public class Section
{
public string Title { get; set; }
private List<string> content = new List<string>();
public List<string> Content
{
get { return content; }
}
}
Load the document, extract the text fragments from the first page and transform them into sections.
PdfFixedDocument document = new PdfFixedDocument(CREC-2014-09-19.pdf");
PdfContentExtractor ce = new PdfContentExtractor(document.Pages[0]);
PdfTextFragmentCollection textFragments = ce.ExtractTextFragments();
List<Section> sections = ProcessSections(textFragments);
UpdateSectionTitle(sections);
Transform text fragments into sections:
public List<Section> ProcessSections(PdfTextFragmentCollection textFragments)
{
List<Section> sections = new List<Section>();
Section currentSection = null;
string currentLine = null;
for (int i = 0; i < textFragments.Count; i++)
{
PdfTextFragment tf = textFragments[i];
if ((tf.Text == "f ") && (tf.PostScriptFontName == "Gpospec5"))
{
// Store the last line of the section that just ended.
if ((currentSection != null) && (currentLine != null))
{
currentSection.Content.Add(currentLine);
}
currentSection = new Section();
sections.Add(currentSection);
currentLine = null;
continue;
}
if (currentSection != null)
{
// Current text fragment has a different baseline from the previous fragment, create a new line.
// Let's consider that if the difference is greater than 1/3 of font size we have a new line.
if (Math.Abs(tf.FragmentCorners[0].Y - textFragments[i - 1].FragmentCorners[0].Y) > tf.TransformedFontSize / 3)
{
if (currentLine != null)
{
// Store the current line.
currentSection.Content.Add(currentLine);
}
// Begin a new line.
currentLine = "";
}
if (currentLine != "")
{
// If the X position of current text fragment is larger with a third of font size than end X position of previous fragment
// then we have a graphic space.
if ((tf.FragmentCorners[0].X - textFragments[i - 1].FragmentCorners[1].X) > tf.TransformedFontSize / 3)
{
currentLine = currentLine + " ";
}
currentLine = currentLine + tf.Text;
}
else
{
currentLine = tf.Text;
}
}
}
return sections;
}
Retrieve section title from content:
private static void UpdateSectionTitle(List<Section> sections)
{
for (int i = 0; i < sections.Count; i++)
{
sections[i].Title = "";
while (sections[i].Content.Count > 0)
{
// If the text is uppercase move it from content to title.
if (IsStringUppercase(sections[i].Content[0]))
{
sections[i].Title += sections[i].Content[0] + " ";
sections[i].Content.RemoveAt(0);
}
else
{
break;
}
}
}
}
, section titles are all caps following the image, and end when encountering non-cap letters.
