C# Requires Chilkat v11.7.0+

Clipped, Off-Page and White-on-White Text in PDF Extraction

See more PDF Text Extraction Examples

Demonstrates the "clippedText", "offPageText" and "obscuredText" filters. Text that a reader never sees - hidden by a clipping path, outside the crop box, or drawn in the same color as the box beneath it - is excluded by default, and the quality report notes what was skipped. Each kind can be included. C#

bool success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  The PDF used in this example is available at hidden_text.pdf

Chilkat.Pdf pdf = new Chilkat.Pdf();
success = pdf.LoadFile("qa_data/pdf/hidden_text.pdf");
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Chilkat.JsonObject json = new Chilkat.JsonObject();
Chilkat.JsonObject jsonOut = new Chilkat.JsonObject();

//  The page has a visible paragraph plus three hidden lines: one drawn outside its clipping
//  rectangle, one below the crop box, and one in white on a white box.
success = pdf.ExtractText("text",json,jsonOut);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("---- default ----");
Debug.WriteLine(jsonOut.StringOf("text"));

//  The quality report says what was left out.
int i = 0;
int count_i = jsonOut.SizeOfArray("quality.pages[0].issues");
while (i < count_i) {
    jsonOut.I = i;
    Debug.WriteLine("issue: " + jsonOut.StringOf("quality.pages[0].issues[i].code"));
    i = i + 1;
}

//  Include everything.
json.UpdateString("clippedText","include");
json.UpdateString("offPageText","include");
json.UpdateString("obscuredText","include");
success = pdf.ExtractText("text",json,jsonOut);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("---- clippedText, offPageText, obscuredText: include ----");
Debug.WriteLine(jsonOut.StringOf("text"));

//  Sample output:

//  ---- default ----
//  Visible Text
//  
//  This paragraph is visible. The page also carries three kinds of text a reader never sees.
//  
//  End of the visible text.
//  issue: obscuredTextSkipped
//  issue: clippedTextSkipped
//  ---- clippedText, offPageText, obscuredText: include ----
//  Visible Text
//  
//  This paragraph is visible. The page also carries three kinds of text a reader never sees.
//  
//  CLIPPED: this line is drawn outside its clipping rectangle.
//  
//  OBSCURED: this line is white on a white box.
//  
//  End of the visible text.
//  
//  OFFPAGE: this line sits below the crop box.