PDF Hidden objects

1
votes

I am studying Marked content in PDF.

I came across one PDF file which has Marked content but few object from marked content are hidden. So here one block of BDC-EMC has both visible and hidden objects. I don't see OCGs array in document. How does this works, how to know which object (graphics/text) is visible and which one is hidden?

I do not see option to attach pdf file here so sharing content stream. Here only one BT-ET block enter code herein "/PlacedPDF /MC0 BDC " is visible all other are hidden.

Any help is highly appreciated.enter code here Thanks!!, Chetan

PDF Content Stream

/Span <</Lang (en)/MCID 1597 >>BDC 
    /Span <</ActualText (þÿ    )>>BDC 
    EMC 
EMC 
/Span <</Lang (en)/MCID 1598 >>BDC 
EMC 
/Span <</Lang (en)/MCID 1599 >>BDC 
    /Span <</ActualText (þÿ    )>>BDC 
   EMC 
EMC

q
    /Perceptual ri
    /GS0 gs
    /T1_1 1 Tf
   /Fm0 Do
Q
/Figure <</MCID 1602 >>BDC 
/PlacedPDF /MC0 BDC 

<------------------------------- START -------------------------------->

BT
0 0 0 1 k
/Perceptual ri
/GS0 gs
/T1_0 1 Tf
6.7092 0 0 6.7092 91.8006 408.647 Tm
[(St)-20(andard)]TJ
ET

<------------------------------- END -------------------------------->


q
67.107 261.154 77 188.188 re
W n
BT
-0.12 Tw 6.7092 0 0 6.7092 332.5724 347.7748 Tm
[(Mec)50(hanical T)115(ee)]TJ
0 Tw 17.697 9.073 Td
[(A)40(WW)40(A Ductile Iron Pipe)]TJ
-34.941 -1.057 Td
[(R)20(educing)]TJ
-1.399 -20.545 Td
(Outlet Coupling)Tj
ET
Q
q
67.107 261.154 77 188.188 re
W n
BT
6.7092 0 0 6.7092 339.3285 306.0237 Tm
[(Saddle-L)20(et)]TJ
-18.251 6.751 Td
[(R)20(educing)]TJ
-4.096 -1.2 Td
(\(2" x 1\275", 2\275" x 2", 3" x 2\275"\))Tj
-0.025 Tw 20.744 8.715 Td
[(Flange A)20(dapter)]TJ
0 Tw 2.279 -20.578 Td
[(W)-20(ildcat)]TJ
19.004 0 Td
(HDPE Pipe)Tj
ET
Q
q
67.107 261.154 77 188.188 re
W n
BT
-0.025 Tw 6.7092 0 0 6.7092 467.048 359.0001 Tm
[(IPS )-25(to A)40(WW)40(A)]TJ
ET
EMC 
EMC 
/Figure <</MCID 1603 >>BDC 
/PlacedPDF /MC1 BDC 
Q
q
170.527 255.484 83.892 188.189 re
W n
BT
6.7092 0 0 6.7092 73.8793 402.9777 Tm
[(St)-20(andard)]TJ
0.205 -7.706 Td
(GapSeal)Tj
-0.12 Tw 35.682 -1.367 Td
[(Mec)50(hanical T)115(ee)]TJ
0 Tw 17.697 9.073 Td
[(A)40(WW)40(A Ductile Iron Pipe)]TJ
ET
Q
q
170.527 255.484 83.892 188.189 re
W n
BT
6.7092 0 0 6.7092 65.2513 303.5076 Tm
[(End P)20(rotection)]TJ
38.18 -0.47 Td
[(Saddle-L)20(et)]TJ
ET
Q
q
170.527 255.484 83.892 188.189 re
W n
BT
-0.025 Tw 6.7092 0 0 6.7092 310.6531 396.0676 Tm
[(Flange A)20(dapter)]TJ
0 Tw 2.279 -20.578 Td
(W)Tj
6.7092 0 0 6.7092 171.4775 337.5969 Tm
24.043 -11.863 Td
(ildcat)Tj
17.984 0 Td
(HDPE Pipe)Tj
-56.203 -0.017 Td
[(F)20(astFit)]TJ
4.1287 0 0 4.1287 96.3529 259.9574 Tm
(\256)Tj
-0.025 Tw 6.7092 0 0 6.7092 449.1268 353.3308 Tm
[(IPS )-25(to A)40(WW)40(A)]TJ
ET
EMC 
EMC 
/Figure <</MCID 1604 >>BDC 
/PlacedPDF /MC2 BDC 
Q
q
62.748 59.87 83.953 188.188 re
W n
BT
6.7092 0 0 6.7092 -157.3332 207.3635 Tm
[(St)-20(andard)]TJ
0.205 -7.706 Td
(GapSeal)Tj
ET
Q
q
62.748 59.87 83.953 188.188 re
W n
BT
6.7092 0 0 6.7092 202.1706 207.3635 Tm
[(A)40(WW)40(A Ductile Iron Pipe)]TJ
-34.941 -1.057 Td
[(R)20(educing)]TJ
-1.399 -20.545 Td
(Outlet Coupling)Tj
-18.53 6.776 Td
[(End P)20(rotection)]TJ
ET
Q
q
62.748 59.87 83.953 188.188 re
W n
BT
6.7092 0 0 6.7092 -32.2543 150.0337 Tm
[(R)20(educing)]TJ
-4.096 -1.2 Td
(\(2" x 1\275", 2\275" x 2", 3" x 2\275"\))Tj
ET
Q
q
62.748 59.87 83.953 188.188 re
W n
BT
6.7092 0 0 6.7092 222.231 62.3919 Tm
(HDPE Pipe)Tj
-56.203 -0.017 Td
[(F)20(astFit)]TJ
4.1287 0 0 4.1287 -134.8597 64.3432 Tm
(\256)Tj
-0.025 Tw 6.7092 0 0 6.7092 217.9142 157.7166 Tm
[(IPS )-25(to A)40(WW)40(A)]TJ
ET
EMC 
EMC 
/Figure <</MCID 1605 >>BDC 
/PlacedPDF /MC3 BDC 
Q
q
169.441 59.898 85.291 183.362 re
W n
BT
6.7092 0 0 6.7092 -181.845 207.3911 Tm
[(St)-20(andard)]TJ
0.205 -7.706 Td
(GapSeal)Tj
-0.12 Tw 35.682 -1.367 Td
[(Mec)50(hanical T)115(ee)]TJ
ET
Q
q
169.441 59.898 85.291 183.362 re
W n
BT
6.7092 0 0 6.7092 -56.7661 200.2995 Tm
[(R)20(educing)]TJ
-1.399 -20.545 Td
(Outlet Coupling)Tj
-18.53 6.776 Td
[(End P)20(rotection)]TJ
38.18 -0.47 Td
[(Saddle-L)20(et)]TJ
-18.251 6.751 Td
[(R)20(educing)]TJ
-4.096 -1.2 Td
(\(2" x 1\275", 2\275" x 2", 3" x 2\275"\))Tj
-0.025 Tw 20.744 8.715 Td
[(Flange A)20(dapter)]TJ
0 Tw 2.279 -20.578 Td
[(W)-20(ildcat)]TJ
ET
Q
q
169.441 59.898 85.291 183.362 re
W n
BT
6.7092 0 0 6.7092 -179.356 62.3054 Tm
[(F)20(astFit)]TJ
4.1287 0 0 4.1287 -159.3715 64.3708 Tm
(\256)Tj
ET
EMC 
EMC 
Q
1
pdfpdf-generationpdf-parsing
"I do not see option to attach pdf file here so sharing content stream." - stack overflow does not itself provide the means for file sharing. Usually, therefore, one uses a third party file sharing service (drop box, google drive, ...), creates a public share there and posts the URL of that share here. Please share the PDF that way. Furthermore, please describe clearer which contents you think unexpectedly hidden. – mkl
Thanks for your reply, here is PDF file that I am trying to parse, in this file if you see only word "Standard" is visible. where are there is more text which is hidden. I am able to parse all text but not able to understand which text is visible and which one is invisible. drive.google.com/file/d/1WP8y0GQBZujdKMNhE7MWSAFvGxJhy3VZ/… – user3500523

1 Answers

2
votes

The text objects (except the first one drawing "Standard") are prepended by a clip path definition their respective text is drawn outside of. Thus, those text pieces are not visible.

For example:

q
67.107 261.154 77 188.188 re
W n
BT
-0.12 Tw 6.7092 0 0 6.7092 332.5724 347.7748 Tm
[(Mec)50(hanical T)115(ee)]TJ
0 Tw 17.697 9.073 Td
[(A)40(WW)40(A Ductile Iron Pipe)]TJ
-34.941 -1.057 Td
[(R)20(educing)]TJ
-1.399 -20.545 Td
(Outlet Coupling)Tj
ET
Q

At the beginning of this block the current clip path is reduced to a rectangle with its lower left corner at (67.107, 261.154) and a size of 77×188.188. The text pieces thereafter are drawn rightwards with approximate baseline starts at

  • (333, 348)
  • (350, 357)
  • (315, 356)
  • (314, 335)

These baseline starts clearly are right of that clip path rectangle, so the text pieces drawn rightwards also are. Thus, they are hidden.