Highlight element in pdf based on coordinates c#

Question

I have 5 pages pdf need to highlight specific element based on coordinates

Have X top left,Y top left,X top right ,Y top right , X bottom right , Y bottom right ,X bottom left, Y bottom left .

I tried below code using iTextsharp please suggest how can we do this including page no

using System;
using System.ComponentModel;
using System.Data;
using System.Text; 
using System.Windows.Forms; 
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;        


//Create a simple test file
string outputFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Test.pdf");

//Create a new file from our test file with highlighting
string highLightFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Highlighted.pdf");

//Bind a reader and stamper to our test PDF
PdfReader reader = new PdfReader(outputFile);

using (FileStream fs = new FileStream(highLightFile, FileMode.Create, FileAccess.Write, FileShare.None))
{
    using (PdfStamper stamper = new PdfStamper(reader, fs))
    {
        //Create a rectangle for the highlight. NOTE: Technically this isn't used but it helps with the quadpoint calculation
        iTextSharp.text.Rectangle rect = new iTextSharp.text.Rectangle(60.6755f, 749.172f, 94.0195f, 735.3f);
        //Create an array of quad points based on that rectangle. NOTE: The order below doesn't appear to match the actual spec but is what Acrobat produces
        float[] quad = { rect.Left, rect.Bottom, rect.Right, rect.Bottom, rect.Left, rect.Top, rect.Right, rect.Top };

        //Create our hightlight
        PdfAnnotation highlight = PdfAnnotation.CreateMarkup(stamper.Writer, rect, null, PdfAnnotation.MARKUP_HIGHLIGHT, quad);

        //Set the color
        highlight.Color = BaseColor.YELLOW;

        //Add the annotation
        stamper.AddAnnotation(highlight,1);
    }
}

Output Highlight element in rectangular. Need to highlight 3rd page of PDF.

"boundingBox": [3.2924,7.7146,5.7564,7.7038,5.7671,7.9836,3.3032,7.9943]

this "text": "66 66 6666 6666" should get higlighted

Input File Output File

*"Need to highlight 3rd page of PDF."*- then why do you add the annotation to page 1? `stamper.AddAnnotation(highlight,1)` — mkl, Jun 03 '19 at 17:47
Thanks mkl but the rectangular box isn't appering is there any formula to calculate `rect.Left, rect.Bottom, rect.Right, rect.Bottom, rect.Left, rect.Top, rect.Right, rect.Top ` this stuff when i am using my coorinates it is occuring at the bottom. — Tony, Jun 04 '19 at 10:29
Your output.pdf does not look like iText 5.x was the final PDF processor manipulating it. Is there probably an annotation flattener that processes the PDF thereafter? — mkl, Jun 04 '19 at 15:52
@mkl `the final PDF processor manipulating?` Yes just for example created sample file Need to point at that segment by using specified boundingBox — Tony, Jun 04 '19 at 16:47
*"Need to point at that segment by using specified boundingBox"* - for that you need to ask the source of that *boundingBox* for the coordinate system assumed. — mkl, Jun 04 '19 at 16:57

mkl · Accepted Answer · 2019-06-04T17:01:19.380

Wrong page

First of all, you add the annotation to the wrong page.

You say

Need to highlight 3rd page of PDF.

but you put it on page 1:

stamper.AddAnnotation(highlight,1);

To fix this, change the page number there:

stamper.AddAnnotation(highlight,3);

Wrong coordinates

Neither the coordinates in your code

iTextSharp.text.Rectangle rect = new iTextSharp.text.Rectangle(60.6755f, 749.172f, 94.0195f, 735.3f);

nor those you gave in that JSON'ish way

"boundingBox": [3.2924,7.7146,5.7564,7.7038,5.7671,7.9836,3.3032,7.9943]

are anywhere near the location you want to highlight, at least not in the regular PDF coordinate system given by the page media box. By measuring in Adobe Acrobat I got the following approximate coordinates:

iTextSharp.text.Rectangle rect = new iTextSharp.text.Rectangle(240f, 264f, 413f, 289f);

If any of the coordinates you showed are meant to be actual coordinates of the image part to highlight, ask the provider of those coordinates about the coordinate system used and accordingly transform to coordinates in the given page's media box.

Questionable order in QuadPoints

You create quad using this order:

float[] quad = { rect.Left, rect.Bottom, rect.Right, rect.Bottom, rect.Left, rect.Top, rect.Right, rect.Top };

This results in concave caps. You probably want to use

float[] quad = { rect.Left, rect.Top, rect.Right, rect.Top, rect.Left, rect.Bottom, rect.Right, rect.Bottom };

instead which Adobe Reader shows as convex caps. For a background read this answer.

Example output

You say:

"66 66 6666 6666" should get higlighted

With the three changes above applied to your code I get this:

Highlight element in pdf based on coordinates c#

1 Answers1

Wrong page

Wrong coordinates

Questionable order in QuadPoints

Example output