pdfpatch

A simple patching tool to modify PDF pages using Ghostscript.

This executes a patch script to overlay opaque masks and text.

It works by executing a custom PostScript /EndPage procedure when showpage is invoked, at the end of each page that needs patching. An alternative is to use annotation pdfmarks or annotator software like mutool but this solution is simple and accurate, and avoids annotations which are not always supported. Note that with Ghostscript V9.21 the -dPreserveAnnots=false switch renders PDF annotations as content stream data.

Usage

gs -q -dNOSAFER -sDEVICE=pdfwrite -o out.pdf -sPDFname=in.pdf -- pdfpatch.ps args
to pass patch arguments on the commandline, or
gs -q -dNOSAFER -sDEVICE=pdfwrite -o out.pdf -sPDFname=in.pdf -sargname=args.txt pdfpatch.ps
to read patch arguments from a script file. Patch arguments are in PostScript dictionary syntax, e.g.:

/page 2 /colour 16#ffee11 /x 20 /y 100 /width 20 /height 5 /operation (rect)
/page 3 /colour 0 /x 21 /y 99 /font (Arial,Italic) /fontsize 11 /text (my text) /operation (write)

Options

File options:
-sPDFname=in.pdf — the PDF file to modify
-o out.pdf — the output PDF file
-sargname=args.txt — the optional patch script file
-dShowFonts — dump all available fonts then quit, e.g. gs -q -dNODISPLAY -dShowFonts pdfpatch.ps
PDF metadata options:
-sPDFtitle='My Title' — set Title
-sPDFauthor='My Name' — set Author
-sPDFsubject='My Subject' — set Subject
Ghostscript options can be used as well, of course, e.g.
-dCompatibilityLevel=1.x — set PDF compatibility to 1.2 or higher
-dCompressPages=false — output uncompressed PDF
-dFILTERIMAGE — remove images

Arguments

These are the patch arguments and default values:

• /from-top true — measure from top of page
• /offset-x 0 — fixed horizontal offest (mm)
• /offset-y 0 — fixed vertical offest (mm)
• /page 1 — page number, 1 to last
• /font (Times-Roman) — font resource name
• /fontsize 12 — point size
• /text () — text to write
• /x 0 — rectangle left or text insert point (mm)
• /y 0 — rectangle bottom or text baseline (mm)
• /width 100 — rectangle width (mm)
• /height 100 — rectangle height (mm)
• /colour 16#000000 — paint colour (RRGGBB)
• /operation null — rect or write

Each patch ends when an /operation value is encountered, then it is cloned for the next patch operation.

Example

This fragment changes words in Old English to modern language for an old hymn:


(The cream rub-out patches would normally be white)
The patch script looks like:

/font (Times-Roman)
/fontsize 12
/page 1

% rects ==================================================

/colour 16#ffffcc % cream
/height 4.5

% verse 3

/y 190.4 % 189.1 + 1.3

% Thou
/x 18
/width 10
/operation (rect)

% shalt
/x 56
/width 10
/operation (rect)

% verse 4

/y 194.6 % 193.3 + 1.3

% Thy
/x 28
/width 9
/operation (rect)

% Thou art
/x 65
/width 17
/operation (rect)

% texts ==================================================

/colour 0 % black

% verse 3

/y 189.1

/x 20
/text (You)
/operation (write)

/x 57
/text (shall)
/operation (write)

% verse 4

/y 193.3

/x 29
/text (your)
/operation (write)

/x 67
/text (you)
/operation (write)

/x 76
/text (are)
/operation (write)