Does anybody know a way to vectorize the text in a PDF document? That is, I want each letter to be a shape/outline, without any textual content. I'm using a Linux system, and open source or a non-Windows solution would be preferred.
The context: I'm trying to edit some old PDFs, for which I no longer have the fonts. I'd like to do it in Inkscape, but that will replace all the fonts with generic ones, and that's barely readable. I've also been converting back and forth using pdf2ps and ps2pdf, but the font info stays there. So when I load it into Inkscape, it still looks awful.
Any ideas? Thanks.
To achieve this, you will have to:
This answer will omit step 3, since that's not programmable.
If you don't want a programmatic way to split documents, the modern way would be with using stapler. In your favorite shell:
stapler burst file.pdf
Would generate {file_1.pdf,...,file_N.pdf}, where 1...N are the PDF pages. Stapler itself uses PyPDF2 and the code for splitting a PDF file is not that complex. The following function splits a file and saves the individual pages in the current directory. (shamelessly copying from the commands.py file)
import math
import os
from PyPDF2 import PdfFileWriter, PdfFileReader
def split(filename):
with open(filename) as inputfp:
inputpdf = PdfFileReader(inputfp)
base, ext = os.path.splitext(os.path.basename(filename))
# Prefix the output template with zeros so that ordering is preserved
# (page 10 after page 09)
output_template = ''.join([
base,
'_',
'%0',
str(math.ceil(math.log10(inputpdf.getNumPages()))),
'd',
ext
])
for page in range(inputpdf.getNumPages()):
outputpdf = PdfFileWriter()
outputpdf.addPage(inputpdf.getPage(page))
outputname = output_template % (page + 1)
with open(outputname, 'wb') as fp:
outputpdf.write(fp)
Now to convert the PDFs to editable files, I'd probably use pdf2svg.
pdf2svg input.pdf output.svg
If we take a look at the pdf2svg.c file, we can see that the code in principle is not that complex (assuming the input filename is in the filename variable and the output file name is in the outputname variable). A minimal working example in python follows. It requires the pycairo and pypoppler libraries:
import os
import cairo
import poppler
def convert(inputname, outputname):
# Convert the input file name to an URI to please poppler
uri = 'file://' + os.path.abspath(inputname)
pdffile = poppler.document_new_from_file(uri, None)
# We only have one page, since we split prior to converting. Get the page
page = pdffile.get_page(0)
# Get the page dimensions
width, height = page.get_size()
# Open the SVG file to write on
surface = cairo.SVGSurface(outputname, width, height)
context = cairo.Context(surface)
# Now we finally can render the PDF to SVG
page.render_for_printing(context)
context.show_page()
At this point you should have an SVG in which all text has been converted to paths, and will be able to edit with Inkscape without rendering issues.
You can call pdf2svg in a for loop to do that. But you would need to know the number of pages beforehand. The code below figures the number of pages and does the conversion in a single step. It requires only pycairo and pypoppler:
import os, math
import cairo
import poppler
def convert(inputname, base=None):
'''Converts a multi-page PDF to multiple SVG files.
:param inputname: Name of the PDF to be converted
:param base: Base name for the SVG files (optional)
'''
if base is None:
base, ext = os.path.splitext(os.path.basename(inputname))
# Convert the input file name to an URI to please poppler
uri = 'file://' + os.path.abspath(inputname)
pdffile = poppler.document_new_from_file(uri, None)
pages = pdffile.get_n_pages()
# Prefix the output template with zeros so that ordering is preserved
# (page 10 after page 09)
output_template = ''.join([
base,
'_',
'%0',
str(math.ceil(math.log10(pages))),
'd',
'.svg'
])
# Iterate over all pages
for nthpage in range(pages):
page = pdffile.get_page(nthpage)
# Output file name based on template
outputname = output_template % (nthpage + 1)
# Get the page dimensions
width, height = page.get_size()
# Open the SVG file to write on
surface = cairo.SVGSurface(outputname, width, height)
context = cairo.Context(surface)
# Now we finally can render the PDF to SVG
page.render_for_printing(context)
context.show_page()
# Free some memory
surface.finish()
To reassemble you can use the pair inkscape / stapler to convert the files manually. But it is not hard to write code that does this. The code below uses rsvg and cairo. To convert from SVG and merge everything into a single PDF:
import rsvg
import cairo
def convert_merge(inputfiles, outputname):
# We have to create a PDF surface and inform a size. The size is
# irrelevant, though, as we will define the sizes of each page
# individually.
outputsurface = cairo.PDFSurface(outputname, 1, 1)
outputcontext = cairo.Context(outputsurface)
for inputfile in inputfiles:
# Open the SVG
svg = rsvg.Handle(file=inputfile)
# Set the size of the page itself
outputsurface.set_size(svg.props.width, svg.props.height)
# Draw on the PDF
svg.render_cairo(outputcontext)
# Finish the page and start a new one
outputcontext.show_page()
# Free some memory
outputsurface.finish()
PS: It should be possible to use the command pdftocairo, but it doesn't seem to call render_for_printing(), which makes the output SVG maintain the font information.