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pdf_to_csv.go
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pdf_to_csv.go
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/*
* PDF to CSV: Example illustrating capability to extract TextMarks from PDF, and grouping together into
* words, rows and columns for CSV data extraction.
*
* Includes debugging capabilities such as outputing a marked up PDF showing bounding boxes of marks,
* words, lines and columns.
*
* Run as: go run pdf_to_csv.go -m all -mf markup.pdf table.pdf table.csv
* - Outputs debug markup including: marks, words, lines, columns to markup.pdf
* - The table data is outputed to table.csv with UTF-8 encoding.
*/
package main
import (
"bytes"
"encoding/csv"
"flag"
"fmt"
"io/ioutil"
"math"
"os"
"sort"
"strings"
"github.com/unidoc/unipdf/v3/common"
"github.com/unidoc/unipdf/v3/contentstream"
"github.com/unidoc/unipdf/v3/core"
"github.com/unidoc/unipdf/v3/creator"
"github.com/unidoc/unipdf/v3/extractor"
"github.com/unidoc/unipdf/v3/model"
)
var saveParams saveMarkedupParams
func main() {
// Make sure to enter a valid license key.
// Otherwise text is truncated and a watermark added to the text.
// License keys are available via: https://unidoc.io
/*
license.SetLicenseKey(`
-----BEGIN UNIDOC LICENSE KEY-----
...key contents...
-----END UNIDOC LICENSE KEY-----
`, "Customer Name")
*/
// Alternatively license can be loaded via UNIPDF_LICENSE_PATH and UNIPDF_CUSTOMER_NAME environment variables,
// where UNIPDF_LICENSE_PATH points to the file containing the license key and the UNIPDF_CUSTOMER_NAME
// the explicitly specified customer name to which the key is licensed.
var (
loglevel string
saveMarkup string
markupPath string
)
flag.StringVar(&loglevel, "l", "info", "Set log level (default: info)")
flag.StringVar(&saveMarkup, "m", "none", "Save markup (none/marks/words/lines/columns/all)")
flag.StringVar(&markupPath, "mf", "/tmp/markup.pdf", "Output markup path (default /tmp/markup.pdf)")
flag.Parse()
args := flag.Args()
if len(args) < 2 {
fmt.Printf("Syntax: go run pdf_to_csv.go [options] <file.pdf> <output.csv>\n")
os.Exit(1)
}
switch loglevel {
case "trace":
common.SetLogger(common.NewConsoleLogger(common.LogLevelTrace))
case "debug":
common.SetLogger(common.NewConsoleLogger(common.LogLevelDebug))
default:
common.SetLogger(common.NewConsoleLogger(common.LogLevelInfo))
}
saveParams = saveMarkedupParams{}
switch saveMarkup {
case "marks":
saveParams.markupType = "marks"
case "words":
saveParams.markupType = "words"
case "lines":
saveParams.markupType = "lines"
case "columns":
saveParams.markupType = "columns"
case "all":
saveParams.markupType = "all"
default:
saveParams.markupType = "none"
}
saveParams.markupOutputPath = markupPath
inPath := args[0]
outPath := args[1]
err := extractTableData(inPath, outPath)
if err != nil {
fmt.Printf("Error: %v\n", err)
os.Exit(1)
}
}
// extractTableData extracts tabular information from PDF file `inPath` and outputs
// the data as CSV file to `outPath`.
func extractTableData(inPath string, outPath string) error {
f, err := os.Open(inPath)
if err != nil {
return fmt.Errorf("Could not open %q err=%v", inPath, err)
}
defer f.Close()
pdfReader, err := model.NewPdfReaderLazy(f)
if err != nil {
return fmt.Errorf("NewPdfReaderLazy failed. %q err=%v", inPath, err)
}
numPages, err := pdfReader.GetNumPages()
if err != nil {
return fmt.Errorf("GetNumPages failed. %q err=%v", inPath, err)
}
saveParams.pdfReader = pdfReader
saveParams.markups = map[int][][]model.PdfRectangle{}
var csvData bytes.Buffer
for pageNum := 1; pageNum <= numPages; pageNum++ {
if pageNum > 3 {
break
}
saveParams.curPage = pageNum
page, err := pdfReader.GetPage(pageNum)
if err != nil {
return fmt.Errorf("GetNumPages failed. %q pageNum=%d err=%v", inPath, pageNum, err)
}
mbox, err := page.GetMediaBox()
if err != nil {
return err
}
if page.Rotate != nil && *page.Rotate == 90 {
// TODO: This is a "hack" to change the perspective of the extractor to account for the rotation.
contents, err := page.GetContentStreams()
if err != nil {
return err
}
cc := contentstream.NewContentCreator()
cc.Translate(mbox.Width()/2, mbox.Height()/2)
cc.RotateDeg(-90)
cc.Translate(-mbox.Width()/2, -mbox.Height()/2)
rotateOps := cc.Operations().String()
contents = append([]string{rotateOps}, contents...)
page.Duplicate()
err = page.SetContentStreams(contents, core.NewRawEncoder())
if err != nil {
return err
}
page.Rotate = nil
}
ex, err := extractor.New(page)
if err != nil {
return fmt.Errorf("NewPdfReaderLazy failed. %q pageNum=%d err=%v", inPath, pageNum, err)
}
pageText, _, _, err := ex.ExtractPageText()
if err != nil {
return fmt.Errorf("ExtractPageText failed. %q pageNum=%d err=%v", inPath, pageNum, err)
}
text := pageText.Text()
textMarks := pageText.Marks()
common.Log.Debug("pageNum=%d text=%d textMarks=%d", pageNum, len(text), textMarks.Len())
group := []model.PdfRectangle{}
for _, mark := range textMarks.Elements() {
group = append(group, mark.BBox)
}
saveParams.markups[pageNum] = append(saveParams.markups[pageNum], group)
pageCSV, err := pageMarksToCSV(textMarks)
if err != nil {
common.Log.Debug("Error grouping text: %v", err)
return err
}
csvData.WriteString(pageCSV)
}
if saveParams.markupType != "none" {
err = saveMarkedupPDF(saveParams)
if err != nil {
return fmt.Errorf("Failed to save marked up pdf: %v", err)
}
}
return ioutil.WriteFile(outPath, csvData.Bytes(), 0666)
}
func rectUnion(b1, b2 model.PdfRectangle) model.PdfRectangle {
return model.PdfRectangle{
Llx: math.Min(b1.Llx, b2.Llx),
Lly: math.Min(b1.Lly, b2.Lly),
Urx: math.Max(b1.Urx, b2.Urx),
Ury: math.Max(b1.Ury, b2.Ury),
}
}
func bboxArea(bbox model.PdfRectangle) float64 {
return math.Abs(bbox.Urx-bbox.Llx) * math.Abs(bbox.Ury-bbox.Lly)
}
// Measure of the difference between areas of `bbox1` and `bbox2` individually
// and that of the union of the two.
func overlaps(bbox1, bbox2 model.PdfRectangle) float64 {
union := rectUnion(bbox1, bbox2)
a := bboxArea(union)
b := bboxArea(bbox1) + bboxArea(bbox2)
diff := (a - b) / (a + b)
return diff
}
// Measure of the vertical overlap of `bbox1` and `bbox2`, when the difference is 0
// then they are exactly on top of each other, and there is overlap when < 0.
func lineOverlap(bbox1, bbox2 model.PdfRectangle) float64 {
union := rectUnion(bbox1, bbox2)
a := math.Abs(union.Ury - union.Lly)
b := math.Abs(bbox1.Ury-bbox1.Lly) + math.Abs(bbox2.Ury-bbox2.Lly)
diff := (a - b) / (a + b)
return diff
}
// Measure of the horizontal overlap of `bbox1` and `bbox2`, when the difference is 0
// then they are exactly on next to each other, and there is overlap when < 0.
func columnOverlap(bbox1, bbox2 model.PdfRectangle) float64 {
union := rectUnion(bbox1, bbox2)
a := math.Abs(union.Urx - union.Llx)
b := math.Abs(bbox1.Urx-bbox1.Llx) + math.Abs(bbox2.Urx-bbox2.Llx)
diff := (a - b) / (a + b)
return diff
}
// Identify lines. - segment words into lines
func identifyLines(words []segmentationWord) [][]segmentationWord {
lines := [][]segmentationWord{}
for _, word := range words {
wbbox, ok := word.BBox()
if !ok {
continue
}
match := false
for i, line := range lines {
firstWord := line[0]
firstBBox, ok := firstWord.BBox()
if !ok {
continue
}
overlap := lineOverlap(wbbox, firstBBox)
common.Log.Debug("'%s'/'%s' overlap: %v [%+v/%+v]", word.String(), firstWord.String(), overlap, wbbox, firstBBox)
if overlap < 0 {
lines[i] = append(lines[i], word)
match = true
break
}
}
if !match {
lines = append(lines, []segmentationWord{word})
}
}
sort.SliceStable(lines, func(i, j int) bool {
bboxi, _ := lines[i][0].BBox()
bboxj, _ := lines[j][0].BBox()
return bboxi.Lly >= bboxj.Lly
})
for li := range lines {
sort.SliceStable(lines[li], func(i, j int) bool {
bboxi, _ := lines[li][i].BBox()
bboxj, _ := lines[li][j].BBox()
return bboxi.Llx < bboxj.Llx
})
}
// Save the line bounding boxes for markup output.
lineGroups := []model.PdfRectangle{}
for li, line := range lines {
var lineRect model.PdfRectangle
common.Log.Trace("Line %d: ", li+1)
for i, word := range line {
wbbox, ok := word.BBox()
if !ok {
continue
}
common.Log.Trace("'%s' / ", word.String())
if i == 0 {
lineRect = wbbox
} else {
lineRect = rectUnion(lineRect, wbbox)
}
}
lineGroups = append(lineGroups, lineRect)
}
saveParams.markups[saveParams.curPage] = append(saveParams.markups[saveParams.curPage], lineGroups)
return lines
}
// Identify columns.
func identifyColumns(words []segmentationWord) []model.PdfRectangle {
columns := [][]segmentationWord{}
for _, word := range words {
wbbox, ok := word.BBox()
if !ok {
continue
}
match := false
bestOverlap := 1.0
bestColumn := 0
for i, column := range columns {
firstWord := column[0]
firstBBox, ok := firstWord.BBox()
if !ok {
continue
}
overlap := columnOverlap(wbbox, firstBBox)
common.Log.Debug("column: '%s'/'%s' overlap: %v [%+v/%+v]", word.String(), firstWord.String(), overlap, wbbox, firstBBox)
if overlap < 0.0 {
if overlap < bestOverlap {
bestOverlap = overlap
bestColumn = i
}
match = true
}
}
if match {
columns[bestColumn] = append(columns[bestColumn], word)
} else {
columns = append(columns, []segmentationWord{word})
}
}
sort.SliceStable(columns, func(i, j int) bool {
bboxi, _ := columns[i][0].BBox()
bboxj, _ := columns[j][0].BBox()
return bboxi.Llx < bboxj.Llx
})
for li := range columns {
sort.SliceStable(columns[li], func(i, j int) bool {
bboxi, _ := columns[li][i].BBox()
bboxj, _ := columns[li][j].BBox()
return bboxi.Lly >= bboxj.Lly
})
}
colGroups := []model.PdfRectangle{}
for li, column := range columns {
var colRect model.PdfRectangle
common.Log.Debug("Column %d: ", li+1)
for i, word := range column {
wbbox, ok := word.BBox()
if !ok {
continue
}
common.Log.Debug(" '%s' / ", word.String())
if i == 0 {
colRect = wbbox
} else {
colRect = rectUnion(colRect, wbbox)
}
}
common.Log.Debug("Column %d: Bbox: %+v", li+1, colRect)
colGroups = append(colGroups, colRect)
}
// Filter by combining overlapping columns.
filtered := []model.PdfRectangle{}
for i := 0; i < len(colGroups); {
colgroup := colGroups[i]
j := i + 1
for ; j < len(colGroups); j++ {
overlap := columnOverlap(colgroup, colGroups[j])
common.Log.Debug("COLUMN overlap %d/%d: %v (%+v/%+v)", i+1, j+1, overlap, colgroup, colGroups[j])
if overlap > 0.0 {
break
}
colgroup = rectUnion(colgroup, colGroups[j])
}
i = j
filtered = append(filtered, colgroup)
}
saveParams.markups[saveParams.curPage] = append(saveParams.markups[saveParams.curPage], filtered)
return filtered
}
// getLineTableTextData converts the lines of words into table strings cells by accounting for
// distribution of lines into columns as specified by `columnBBoxes`.
func getLineTableTextData(lines [][]segmentationWord, columnBBoxes []model.PdfRectangle) [][]string {
tabledata := [][]string{}
for _, line := range lines {
linedata := make([]string, len(columnBBoxes))
for _, word := range line {
wordBBox, ok := word.BBox()
if !ok {
continue
}
bestColumn := 0
bestOverlap := 1.0
for icol, colBBox := range columnBBoxes {
overlap := columnOverlap(wordBBox, colBBox)
if overlap < bestOverlap {
bestOverlap = overlap
bestColumn = icol
}
}
linedata[bestColumn] += word.String()
}
tabledata = append(tabledata, linedata)
}
return tabledata
}
// segmentationWord represents a word that has been segmented in PDF text.
type segmentationWord struct {
ma *extractor.TextMarkArray
}
func (w segmentationWord) Elements() []extractor.TextMark {
return w.ma.Elements()
}
func (w segmentationWord) BBox() (model.PdfRectangle, bool) {
return w.ma.BBox()
}
func (w segmentationWord) String() string {
if w.ma == nil {
return ""
}
var buf bytes.Buffer
for _, m := range w.Elements() {
buf.WriteString(m.Text)
}
return buf.String()
}
// pageMarksToCSV converts textMarks from a single page into CSV by grouping the marks into
// words, lines and columns and then writing the table cells data as CSV output.
func pageMarksToCSV(textMarks *extractor.TextMarkArray) (string, error) {
// STEP - Form words.
// Group the closest text marks that are overlapping.
words := []segmentationWord{}
word := segmentationWord{ma: &extractor.TextMarkArray{}}
var lastMark extractor.TextMark
isFirst := true
for i, mark := range textMarks.Elements() {
if mark.Text == "" {
continue
}
common.Log.Debug("Mark %d - '%s' (% X)", i, mark.Text, mark.Text)
if isFirst {
word = segmentationWord{ma: &extractor.TextMarkArray{}}
word.ma.Append(mark)
lastMark = mark
isFirst = false
continue
}
common.Log.Debug(" - overlaps: %f", overlaps(mark.BBox, lastMark.BBox))
overlap := overlaps(mark.BBox, lastMark.BBox)
if overlap > 0.1 {
if len(strings.TrimSpace(word.String())) > 0 {
common.Log.Debug("Appending word: '%s' (%d chars) (%d elements)", word.String(), len(word.String()), len(word.Elements()))
words = append(words, word)
}
word = segmentationWord{ma: &extractor.TextMarkArray{}}
}
word.ma.Append(mark)
lastMark = mark
}
if len(strings.TrimSpace(word.String())) > 0 {
common.Log.Debug("Appending word: '%s' (%d chars) (%d elements)", word.String(), len(word.String()), len(word.Elements()))
words = append(words, word)
}
// Include the words in the markup.
{
wbboxes := []model.PdfRectangle{}
for _, word := range words {
wbbox, ok := word.BBox()
if !ok {
continue
}
wbboxes = append(wbboxes, wbbox)
}
saveParams.markups[saveParams.curPage] = append(saveParams.markups[saveParams.curPage], wbboxes)
}
lines := identifyLines(words)
// Filter out words in lines with only 1 column.
tableLines := [][]segmentationWord{}
for _, line := range lines {
if len(line) <= 1 {
continue
}
tableLines = append(tableLines, line)
}
tableWords := []segmentationWord{}
for _, line := range tableLines {
for _, word := range line {
tableWords = append(tableWords, word)
}
}
columnBBoxes := identifyColumns(tableWords)
tabledata := getLineTableTextData(lines, columnBBoxes)
var buf bytes.Buffer
w := csv.NewWriter(&buf)
err := w.WriteAll(tabledata)
if err != nil {
return "", err
}
w.Flush()
return buf.String(), nil
}
type saveMarkedupParams struct {
pdfReader *model.PdfReader
markups map[int][][]model.PdfRectangle
curPage int
markupType string
markupOutputPath string
}
// Saves a marked up PDF with the original with certain groups highlighted: marks, words, lines, columns.
func saveMarkedupPDF(params saveMarkedupParams) error {
var pageNums []int
for pageNum, _ := range params.markups {
pageNums = append(pageNums, pageNum)
}
sort.Ints(pageNums)
if len(pageNums) == 0 {
return nil
}
// Make a new PDF creator.
c := creator.New()
for _, pageNum := range pageNums {
common.Log.Debug("Page %d - %d marks", pageNum, len(params.markups[pageNum]))
page, err := params.pdfReader.GetPage(pageNum)
if err != nil {
return fmt.Errorf("saveOutputPdf: Could not get page pageNum=%d. err=%v", pageNum, err)
}
mediaBox, err := page.GetMediaBox()
if err != nil {
return fmt.Errorf("saveOutputPdf: Could not get MediaBox pageNum=%d. err=%v", pageNum, err)
}
if page.MediaBox == nil {
// Deal with MediaBox inherited from Parent.
common.Log.Info("MediaBox: %v -> %v", page.MediaBox, mediaBox)
page.MediaBox = mediaBox
}
h := mediaBox.Ury
if err := c.AddPage(page); err != nil {
return fmt.Errorf("AddPage failed err=%v ", err)
}
colors := map[int]string{
0: "hide", // marks
1: "hide", // words
2: "hide", // lines
3: "hide", // columns
}
switch saveParams.markupType {
case "marks":
colors[0] = "#0000ff"
case "words":
colors[1] = "#00ff00"
case "lines":
colors[2] = "#ff0000"
case "columns":
colors[3] = "#f0f000"
case "all":
colors[0] = "#0000ff"
colors[1] = "#00ff00"
colors[2] = "#ff0000"
colors[3] = "#f0f000"
}
for gi, group := range params.markups[pageNum] {
if colors[gi] == "hide" {
continue
}
borderColor := creator.ColorRGBFromHex(colors[gi])
for i, r := range group {
common.Log.Trace("Mark %d", i+1)
rect := c.NewRectangle(r.Llx, h-r.Lly, r.Urx-r.Llx, -(r.Ury - r.Lly))
rect.SetBorderColor(borderColor)
rect.SetBorderWidth(1.0)
err = c.Draw(rect)
if err != nil {
return fmt.Errorf("Draw failed. pageNum=%d err=%v", pageNum, err)
}
}
}
}
c.SetOutlineTree(params.pdfReader.GetOutlineTree())
if err := c.WriteToFile(saveParams.markupOutputPath); err != nil {
return fmt.Errorf("WriteToFile failed. err=%v", err)
}
common.Log.Info("Saved marked-up PDF file: %v", saveParams.markupOutputPath)
return nil
}