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main.go
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main.go
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package main
import (
"bytes"
"fmt"
"io"
"os"
"path/filepath"
"sort"
"strconv"
"github.com/tdewolff/argp"
)
type Extract struct {
Info bool `desc:"Get document information"`
Page int `short:"p" default:"0" desc:"Page"`
Password string `default:"" desc:"Password"`
Input string `index:"0" desc:"Input file"`
}
type Replace struct {
Page int `short:"p" default:"0" desc:"Page"`
XObj string `desc:"XObject"`
Index int `short:"i" default:"-1" desc:"String index to replace"`
String string `short:"s" desc:"Text replacement"`
XOffset int `desc:"Text X-offset in font units"`
Spacing string `default:"none" desc:"Character spacing type, 'none' for regular spacing, a number for character spacing"`
Password string `default:"" desc:"Password"`
Output string `short:"o" desc:"Output file"`
Input string `index:"0" desc:"Input file"`
}
func main() {
root := argp.NewCmd(&Extract{}, "PDF text extraction and replacement toolkit by Taco de Wolff")
root.AddCmd(&Replace{}, "replace", "Replace text")
root.Parse()
root.PrintHelp()
}
func (cmd *Extract) Run() error {
if cmd.Input == "" {
return argp.ShowUsage
}
f, err := os.Open(cmd.Input)
if err != nil {
return err
}
pdf, err := NewPDFReader(f, cmd.Password)
if err != nil {
return err
}
if cmd.Info {
fmt.Println("File name:", filepath.Base(cmd.Input))
fmt.Println("Pages:", len(pdf.kids))
if _, ok := pdf.trailer["Encrypt"]; ok {
fmt.Println("Encrypted: yes")
} else {
fmt.Println("Encrypted: no")
}
fmt.Println(pdf.GetInfo())
return nil
}
names, objects := getObjects(pdf, cmd.Page)
for i, obj := range objects {
if i == 0 {
fmt.Printf("Page %d:\n", cmd.Page)
} else {
fmt.Printf("\nXObject %s:\n", names[i])
}
err = walkStrings(pdf, obj, func(_, _, index int, state textState, op string, vals []interface{}) (int, error) {
var s string
if op == "TJ" && len(vals) == 1 {
if array, ok := vals[0].(pdfArray); ok {
for _, item := range array {
if val, ok := item.([]byte); ok {
s += state.fonts[state.fontName].ToUnicode(val)
}
}
}
} else if (op == "Tj" || op == "'") && len(vals) == 1 {
if str, ok := vals[0].([]byte); ok {
s = state.fonts[state.fontName].ToUnicode(str)
}
} else if op == "\"" && len(vals) == 3 {
if str, ok := vals[2].([]byte); ok {
s = state.fonts[state.fontName].ToUnicode(str)
}
}
//if names[i] != "" {
// fmt.Printf("xobj=%s ", names[i])
//}
fmt.Printf("i=%4d font=%v: %s\n", index, state.fontName, s)
return 0, nil
})
if err != nil {
return err
}
}
return nil
}
func (cmd *Replace) Run() error {
if cmd.Input == "" {
return argp.ShowUsage
} else if cmd.Index == -1 {
fmt.Println("ERROR: must specify string index to replace")
return argp.ShowUsage
} else if cmd.Output == "" {
cmd.Output = cmd.Input
}
fr, err := os.Open(cmd.Input)
if err != nil {
return err
}
pdf, err := NewPDFReader(fr, cmd.Password)
if err != nil {
fr.Close()
return err
}
var obj interface{}
names, objects := getObjects(pdf, cmd.Page)
for i, name := range names {
if name == cmd.XObj {
obj = objects[i]
break
}
}
if obj == nil {
fr.Close()
return fmt.Errorf("ERROR: unknown object: %s", cmd.XObj)
}
ref, _, stream, err := getContents(pdf, obj)
if err != nil {
fr.Close()
return fmt.Errorf("ERROR: %s", err)
}
err = walkStrings(pdf, obj, func(start, end, index int, state textState, op string, vals []interface{}) (int, error) {
if index == cmd.Index {
s := state.fonts[state.fontName].FromUnicode(cmd.String)
b := bytes.Buffer{}
if op == "'" {
b.WriteString("T*")
} else if op == "\"" && len(vals) == 3 {
pdfWriteVal(&b, nil, pdfRef{}, vals[0])
b.WriteString(" Tw ")
pdfWriteVal(&b, nil, pdfRef{}, vals[1])
b.WriteString(" Tc T*")
}
array := pdfArray{}
if cmd.XOffset != 0 {
array = append(array, -cmd.XOffset)
}
if space, err := strconv.ParseInt(cmd.Spacing, 10, 64); err == nil {
di := state.fonts[state.fontName].Bytes()
for i := 0; i < len(s)-di; i += di {
array = append(array, s[i:i+di], -space)
}
array = append(array, s[len(s)-di:])
} else {
array = append(array, string(s))
}
pdfWriteVal(&b, nil, pdfRef{}, array)
b.WriteString(" TJ")
fmt.Println("Old:", string(stream.data[start:end]))
fmt.Println("New:", b.String())
n := b.Len() - (end - start)
stream.data = append(stream.data[:start], append(b.Bytes(), stream.data[end:]...)...)
return n, io.EOF
}
return 0, nil
})
if err != nil {
fr.Close()
return err
}
fr.Close()
fw, err := os.Create(cmd.Output)
if err != nil {
return err
}
pdfWriter := NewPDFWriter(fw, pdf)
pdfWriter.SetObject(ref, stream)
return pdfWriter.Close()
}
type textState struct {
fonts map[pdfName]pdfFont
fontName pdfName
}
func getObjects(pdf *pdfReader, page int) ([]string, []interface{}) {
dict, _, err := pdf.GetPage(page)
if err != nil {
return []string{}, []interface{}{}
}
names := []string{""}
objects := []interface{}{
dict,
}
var addDict func(string, pdfDict)
addDict = func(prefix string, dict pdfDict) {
resources, _ := pdf.GetDict(dict["Resources"])
xobjects, _ := pdf.GetDict(resources["XObject"])
xnames := []string{}
for name := range xobjects {
xnames = append(xnames, name)
}
sort.Strings(xnames)
if prefix != "" {
prefix += "/"
}
for i, xname := range xnames {
name := fmt.Sprintf("%s%d", prefix, i+1)
xobject, err := pdf.GetStream(xobjects[xname])
if _, ok := xobjects[xname].(pdfRef); ok && err == nil {
if subtype, ok := xobject.dict["Subtype"].(pdfName); ok && (subtype == pdfName("Form") || subtype == pdfName("PS")) {
names = append(names, name)
objects = append(objects, xobjects[xname])
}
}
addDict(name, xobject.dict)
}
}
addDict("", dict)
return names, objects
}
func getContents(pdf *pdfReader, obj interface{}) (pdfRef, pdfDict, pdfStream, error) {
if _, ok := obj.(pdfRef); !ok {
if page, err := pdf.GetDict(obj); err == nil {
if contents, ok := page["Contents"].(pdfArray); ok {
if len(contents) != 1 {
return pdfRef{}, pdfDict{}, pdfStream{}, fmt.Errorf("Contents must be a reference or an array of one element")
}
obj = contents[0]
} else {
obj = page["Contents"]
}
stream, err := pdf.GetStream(obj)
return obj.(pdfRef), page, stream, err
} else {
return pdfRef{}, pdfDict{}, pdfStream{}, fmt.Errorf("object is not a stream or page dictionary")
}
if _, ok := obj.(pdfRef); !ok {
return pdfRef{}, pdfDict{}, pdfStream{}, fmt.Errorf("object is not a stream or page dictionary with a reference")
}
}
stream, err := pdf.GetStream(obj)
return obj.(pdfRef), stream.dict, stream, err
}
func walkStrings(pdf *pdfReader, obj interface{}, cb func(int, int, int, textState, string, []interface{}) (int, error)) error {
state := textState{
fonts: map[pdfName]pdfFont{},
}
var dict pdfDict
var data []byte
if _, page, stream, err := getContents(pdf, obj); err == nil {
dict = page
data = stream.data
} else {
return err
}
i := 0
stream := newPDFStreamReader(data)
for {
start := moveWhiteSpace(data, stream.Pos())
op, vals, err := stream.Next()
if err == io.EOF {
break
} else if err != nil {
return err
}
if op == "Tf" && len(vals) == 2 {
if name, ok := vals[0].(pdfName); ok {
if _, ok := state.fonts[name]; !ok {
state.fonts[name], err = pdf.GetFont(dict, name)
if err != nil {
return err
}
}
state.fontName = name
}
} else if op == "Tj" || op == "TJ" || op == "'" || op == "\"" {
d, err := cb(start, stream.Pos(), i, state, op, vals)
if err == io.EOF {
return nil
} else if err != nil {
return err
}
i += d + 1
} else {
//fmt.Println("unknown operator:", op)
}
}
return nil
}