Edit binary data in PDF with SED / BBE (change colors in a PDF)

I want to change some background colors in a batch of PDF's

I found out that the color information is stored in the first stream - endstream block<br/>
in a format like such: 1 1 1 sc which in this example represents white #FFFFFF

here an example after I decode the binary stream with<br/>
qpdf --qdf --object-streams=disable IN.pdf OUT.pdf

<pre>stream
q Q q /Cs1 cs 0.9686275 0.9725490 0.9764706 sc 0 12777 m 600 12777 l 600 0
l 0 0 l h f 0 12777 m 600 12777 l 600 0 l 0 0 l h f ➡️1 1 1 sc⬅️ 0 12575 m 600
12575 l 600 12308 l 0 12308 l h f 0.1254902 0.2666667 0.3921569 sc 0 872 m
600 872 l 600 462 l 0 462 l h f 0 462 m 600 462 l 600 0 l 0 0 l h f ➡️1 1 1
sc⬅️ 0 12297 m 600 12297 l 600 5122 l 0 5122 l h f 0.7411765 0.8980392 0.9725490
sc 23 7249 m 577 7249 l 577 6007 l 23 6007 l h f 1 0.9215686 0.9333333 sc
23 5848 m 577 5848 l 577 5533 l 23 5533 l h f 0.9686275 0.9725490 0.9764706
sc 23 5510 m 577 5510 l 577 5156 l 23 5156 l h f ➡️1 1 1 sc⬅️ 0 5110 m 600 5110
...
endstream
</pre>

If I open the PDF in TextEdit and manually replace 1 1 1 sc with 0 1 0 sc my white background immediately changes to green after saving the PDF file.

How can I do this in an automated way with a Text Tool?

1. sed 's/1 1 1 sc/0 1 0 sc/' IN.pdf > OUT.pdf<br/>
   gives me the error: sed: RE error: illegal byte sequence

2. bbe -e 's/0 1 1 sc/0 1 0 sc/' IN.pdf > OUT.pdf<br/>
   no errors, OUT.pdf is written but no colors have changed<br/>
   echo 'hello 1 1 1 sc world' | bbe -e 's/1 1 1 sc/0 1 0 sc/'
   seems to work fine...

In the above stream (the first stream block) in the 1-page PDF file I need to replace only the second and third find. The second one has a line break?

It is not completely clear what you are doing.

You mention commands:

qpdf --qdf --object-streams=disable IN.pdf OUT.pdf

sed 's/1 1 1 sc/0 1 0 sc/' IN.pdf > OUT.pdf

bbe -e 's/0 1 1 sc/0 1 0 sc/' IN.pdf > OUT.pdf

It is not obvious if IN.pdf in the sed or bbe commands is the same IN.pdf file as the qpdf command.

If all three commands are using the same file as input, then that can explain why bbe fails.

Another possibility is that the bbe command shown is the command you are actually using and not a typo. It does not actually look for the string 1 1 1 sc.

sed is not designed to work with binary data.
Although the GNU implementation has a non-standard -z option to help read binary files, it still works on a form of "lines". Perl can be used as an improved sed here.

To change only the first three instances of the string 1 1 1 sc in the file, you could try:

qpdf --qdf --object-streams=disable IN.pdf - |\
perl -0777 -pe 'for $i (1..3) { s/1 1 1 sc/0 1 0 sc/ }' |\
qpdf - OUT.pdf

In this Perl command:

• -0777 - treat entire input as single record
• -pe - run command on each record, then print (like sed)
• for $i (1..3) { ... } - run three times
• s/.../.../ - similar to sed's s/// command

I think I will tackle this task with PikePDF, a Python library which seems to be able to work with content streams: https://pikepdf.readthedocs.io/en/latest/topics/content_streams.html

I was just able to Pretty Print the content streams by using:

#!/usr/bin/env python

from pikepdf import Pdf
import pikepdf

with pikepdf.open('IN.pdf') as pdf:
	page 		 = pdf.pages[0]
	instructions = pikepdf.parse_content_stream(page)
	data 		 = pikepdf.unparse_content_stream(instructions)
	print(data.decode('ascii'))

Now working my way to actual Edit the content stream ..........

Here the stream fragment from my question, pretty printed:

q
Q
q
/Cs1 cs
0.9686275 0.9725490 0.9764706 sc
0 12777 m
600 12777 l
600 0 l
0 0 l
h
f
0 12777 m
600 12777 l
600 0 l
0 0 l
h
f
➡️1 1 1 sc⬅️
0 12575 m
600 12575 l
600 12308 l
0 12308 l
h
f
0.1254902 0.2666667 0.3921569 sc
0 872 m
600 872 l
600 462 l
0 462 l
h
f
0 462 m
600 462 l
600 0 l
0 0 l
h
f
➡️1 1 1 sc⬅️
0 12297 m
600 12297 l
600 5122 l
0 5122 l
h
f
0.7411765 0.8980392 0.9725490 sc
23 7249 m
577 7249 l
577 6007 l
23 6007 l
h
f
1 0.9215686 0.9333333 sc
23 5848 m
577 5848 l
577 5533 l
23 5533 l
h
f
0.9686275 0.9725490 0.9764706 sc
23 5510 m
577 5510 l
577 5156 l
23 5156 l
h
f
➡️1 1 1 sc⬅️
0 5110 m
600 5110

Some more info about the color value:
Just divide the RGB values by 255<br/>
for example:

DeepSkyBlue = #00bfff = RGB(0, 191, 255)<br/>
0/255 = 0<br/>
191/255 = 0.7490196<br/>
255/255 = 1<br/>

0 0.7490196 1 sc