用于拆解和组合PDF中各个对象的shell脚本
拆解脚本
header_start=0 header_len=15 xref_start=$(strings -a -t d $1 | grep -e "\bxref\b" | awk '{print $1}') trailer_start=$(strings -a -t d $1 | grep -e "\btrailer\b" | awk '{print $1}') #echo $xref_start #echo $trailer_start xref_len=$(echo "$trailer_start - $xref_start" | bc) #echo $xref_len header_dump=$(echo "$1" | sed -re 's/^(.*)\.pdf/tdis\_\1\_header\.bin/g') dd if=$1 of=$header_dump bs=1 skip=$header_start count=$header_len xref_dump=$(echo "$1" | sed -re 's/^(.*)\.pdf/tdis\_\1\_xref\.bin/g') dd if=$1 of=$xref_dump bs=1 skip=$xref_start count=$xref_len trailer_dump=$(echo "$1" | sed -re 's/^(.*)\.pdf/tdis\_\1\_trailer\.bin/g') dd if=$1 of=$trailer_dump bs=1 skip=$trailer_start #cat tdis_"$1"_xref.bin | awk 'NF==3' | awk 'NR!=1{printf("%d 0 obj is at offset: %d\n", NR-1, $1);}' cat $xref_dump | awk 'NF==3' | awk 'NR!=1{printf("%08d %08d\n", $1, NR-1);}' | sort > tdis_"$xref_dump" #echo "$xref_start 0" >> tdis_"$xref_dump" printf "%08d %08d\n" $xref_start 0 >> tdis_"$xref_dump" cat tdis_$xref_dump | awk 'BEGIN{loffset=0;lobjnum=0;}{printf("%3d %3d %3d\n", loffset, $1-loffset, lobjnum);loffset=$1;lobjnum=$2;}' | awk 'NR!=1' > tdis_metrics_"$xref_dump" if [ ! -d objects ] then mkdir objects fi cat tdis_metrics_"$xref_dump" | while read offset len objn do #echo $offset, $len, $objn obj_name=$(printf "%s_%03d" $1 $objn | sed -re 's/^(.*)\.pdf/tdis\_\1\_obj/g' | awk '{printf("objects/%s.bin", $0);}') #echo $obj_name dd if=$1 of=$obj_name bs=1 skip=$offset count=$len done
组合脚本
target=$1 dd if=$(ls -1 | grep "header.bin") of=$target bs=1 count=15 obj_offset=15 obj_nums=0 for file in $(ls -1 objects) do #echo $file obj_len=$(wc objects/$file | awk '{print $3}') dd if=objects/$file of=$target bs=1 count=$obj_len seek=$obj_offset printf "%010d %05d n\n" $obj_offset 0 >> "tas_generated_"$1"_xref.bin" obj_offset=$[ $obj_offset + $obj_len ] obj_nums=$[ $obj_nums + 1 ] done echo "xref" >> $target printf "0 %d\n" $obj_nums >> $target echo "0000000000 65535 f" >> $target cat "tas_generated_"$1"_xref.bin" >> $target awk 'NR<=2' $(ls -1 | grep "trailer.bin") >> $target echo "startxref" >> $target echo $obj_offset >> $target echo "%%EOF" >> $target
这样,我们就可以对解析出来的单个pdf对象进行单独操作了。
手动找出包含graphic operators stream的对象,使用下面脚本解压stream
target=$(ls -1 objects | grep "_obj_"$1".bin") grep -Ubo --binary-file=text stream objects/$target | sed -e 's/:/ /g' | awk 'NR==1{printf("%d ",$1+7);}NR==2{printf("%d ", $1-10);}' > tdeflate_stream.bin read xstart xend < tdeflate_stream.bin dd if=objects/$target of=flated.bin bs=1 skip=$xstart count=$[ $xend - $xstart ] cat flated.bin | zlib-flate -uncompress > deflated.bin
重新编辑deflated.bin文件,再使用下面脚本压缩
printf "%d 0 obj\n" $1 > tflate_"$1".bin printf "<</Length %d/Filter/FlateDecode>>stream\n" >> tflate_"$1".bin cat deflated.bin | zlib-flate -compress >> tflate_"$1".bin echo "" >> tflate_"$1".bin echo "endstream" >> tflate_"$1".bin echo "endobj" >> tflate_"$1".bin target=$(ls -1 objects | grep "_obj_"$1".bin") rm objects/$target mv tflate_"$1".bin objects/$target