Replacing vector images in a PDF with raster image

问题:

Is there any easy (scriptable) way to convert a PDF with vector images into a PDF with raster images? In other words, I want to generate a PDF with the exact same (un-rasterized) text but with each vector image replaced with a rasterized version.

I occasionally read PDFs of technical articles on my Kindle, and have found that reading a PDF directly is frustrating. Thankfully, Amazon's automatic conversion of PDFs to the Kindle format does a good job of reflowing the text portions of most of PDFs I have tried. However, while raster images seem to make it through the conversion process fine, vector images get horribly mangled. It would be great if I could easily convert a PDF so that all of its vector images were rasterized.

I am interested in any possible solutions, but a Linux- or Windows-based one would be preferable.

回答1:

I had a similar issue, and solved it using ImageMagics convert tool (http://www.imagemagick.org/script/index.php). That comes with linux and runs fine on Windows/Cygwin or OS X

convert -density 300 largeVectorFileFromR.pdf out.pdf

With -density 300 you control resolution (as DPI).

Downside: Text is rasterized as well, I understand that Michael does not want this.

回答2:

After some days searching for some solution, based on "Remove all text from PDF file" and "How to add a picture onto an existing pdf file?" I found a (ugly) scriptable solution:

gs -o /tmp/onlytxt.pdf -sDEVICE=pdfwrite -dFILTERVECTOR -dFILTERIMAGE $INPUT_FILE && \
gs -o /tmp/graphics.pdf -sDEVICE=pdfwrite -dFILTERTEXT $INPUT_FILE && \
convert -density $DPI -quality 100 /tmp/graphics.pdf /tmp/graphics.png && \
convert -density $DPI -quality 100 /tmp/graphics.png /tmp/graphics.pdf && \
pdftk /tmp/graphics.pdf stamp /tmp/onlytxt.pdf output $OUTPUT_FILE && \
rm /tmp/onlytxt.pdf /tmp/graphics.pdf /tmp/graphics.png

were we have three variables INPUT_FILE, OUTPUT_FILE, and DPI. We split the textual and graphical contents via Ghostscript, convert the graphical image to a raster image (PNG) and join the two using pdftk.

I've been using this successfully to convert huge vector images for use in scientific papers.

回答3:

It's a little complicated, but you asked for any possible solution. Furthermore this solution is not automatable.

1) Open the pdf with the vector images in Inkscape. Then select the whole image with the select tool (F1)

2) If the vector image is consistant of more than one svg graphic press Ctrl + G (Object --> Group)

3) cut the grouped svg image Ctrl + x

4) open a new InkScape Window Ctrl + n and paste the image Ctrl + v

5) choose File --> export Bitmap (Shift + Ctrl + e), maybe you want to increase the dpi

6) go back to the first InkScape window, File --> import (Ctrl + i) and choose the previously exported bitmap

7) place the bitmap to the location where the svg image was

Save the pdf and the vector image is replaced by a bitmap image.

回答4:

Pitstop Pro v2 update 3 from Enfocus can do exactly that. It has an action called "Rasterize page content, keeping text" which works pretty well. It is a plugin to Adobe Acrobat so it requires a little more but is also available as a server solution.

回答5:

Here's one way to solve your problem:

Step 1: Use an online PDF-to-HTML converter, like the one here:

http://www.idrsolutions.com/online-pdf-to-html5-converter/

This tool converts the PDF into a set of images and a text overlay. The vector images should be converted to raster at this point.

Step 2: Convert the HTML+images back into PDF:

http://pdfcrowd.com/#convert_by_upload+with_options

The resulting PDF will have all the vector images rasterized, and all text will remain text, so you can select, copy, etc.

回答6:

Convert the pdf to djvu with https://jwilk.net/software/pdf2djvu converter. Uncheck "antialias fonts,vectors..". It will reduce file size significantly and improve document load times.

回答7:

I used the following:

gswin32c -o "%2" -dFirstPage=1 -dLastPage=1 -sDEVICE=pngalpha -r72x72 -dUseCropBox -dFitPage "%1" -dBATCH -dNOPAUSE

where %1 is the input file and %2 is the output. This can be used with LaTeX, the generated PNG has the same ratio and page size as the original PDF so the relative position of the image will not change.

Note that in Linux, you may need to use gs rather than gswin32c.

You can also set the page range and then print the pages back to PDF. The downside is that the text gets rasterized as well.

回答8:

inkscape is the best solution, I quickly made this rather unoptimized batch file that does exactly that and you can play with it and change options. ImageMacick convert, gs, or pdftoimages don't work as good as inkscape they either don't export the layers or export but with bad quality :

#!/bin/bash
#set -xev
ORIGINAL_FOLDER=`pwd` 
JPEGS=`mktemp -d`
unzip "$1" -d "$JPEGS"
cd "$JPEGS"
# expang the pdf in pdf pages
pdftk combined_to_do.pdf burst output pg_%04d.pdf
#1) print the pdf's to pngs as they are seen with alpha, layers, transparency etc, this cannot be done by ImageMacick convert or pdftoimages
ls ./pg*.pdf | xargs -L1 -I {}  inkscape {} -z --export-dpi=300 --export-area-drawing --export-png={}.png
#2) Second change to jpgs
rm *.pdf
ls ./p*.png | xargs -L1 -I {} convert {}  -quality 100 -density 300  {}.jpg
#3) This to make a pdf file out of every jpg image without loss of either resolution or quality:
ls -1 ./*jpg | xargs -L1 -I {} img2pdf {} -o {}.pdf
#4) This to concatenate the pdfpages into one:
pdftk *.jpg.pdf cat output combined.pdf
#5) And last I add an OCRed text layer that doesn't change the quality of the scan in the pdfs so they can be searchable:
pypdfocr combined.pdf
cp "$JPEGS/combined_ocr.pdf" "$ORIGINAL_FOLDER/$1_ocr.pdf"
cp "$JPEGS/combined.pdf" "$ORIGINAL_FOLDER/$1.pdf"