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In text extraction, split lines with tolerance on y coordinate.

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This commit is contained in:
Peter Williams 2018-11-28 22:13:56 +11:00
parent 6529b42a70
commit ad83b1c948
1 changed files with 12 additions and 11 deletions
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23
pdf/extractor/text.go
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@ -781,9 +781,14 @@ func (tl TextList) height() float64 {
func (tl TextList) ToText() string {
tl.printTexts("ToText: before sorting")
tl.SortPosition()
fontHeight := tl.height()
// We sort with a y tolerance to allow for subscripts, diacritics etc.
tol := min(fontHeight*0.2, 5.0)
common.Log.Trace("ToText: fontHeight=%.1f tol=%.1f", fontHeight, tol)
lines := tl.toLines()
tl.SortPosition(tol)
lines := tl.toLines(tol)
texts := []string{}
for _, l := range lines {
texts = append(texts, l.Text)
@ -794,11 +799,7 @@ func (tl TextList) ToText() string {
// SortPosition sorts a text list by its elements' position on a page.
// Sorting is by orientation then top to bottom, left to right when page is orientated so that text
// is horizontal.
func (tl *TextList) SortPosition() {
fontHeight := tl.height()
// We sort with a y tolerance to allow for subscripts, diacritics etc.
tol := min(fontHeight*0.2, 5.0)
common.Log.Trace("SortPosition: fontHeight=%.1f tol=%.1f", fontHeight, tol)
func (tl *TextList) SortPosition(tol float64) {
sort.SliceStable(*tl, func(i, j int) bool {
ti, tj := (*tl)[i], (*tl)[j]
if ti.Orient != tj.Orient {
@ -822,7 +823,7 @@ type Line struct {
// toLines returns the text and positions in `tl` as a slice of Line.
// NOTE: Caller must sort the text list top-to-bottom, left-to-write (for orientation adjusted so
// that text is horizontal) before calling this function.
func (tl TextList) toLines() []Line {
func (tl TextList) toLines(tol float64) []Line {
// We divide `tl` into slices which contain texts with the same orientation, extract the lines
// for each orientation then return the concatention of these lines sorted by orientation.
tlOrient := map[int]TextList{}
@ -831,7 +832,7 @@ func (tl TextList) toLines() []Line {
}
lines := []Line{}
for _, o := range orientKeys(tlOrient) {
lines = append(lines, tlOrient[o].toLinesOrient()...)
lines = append(lines, tlOrient[o].toLinesOrient(tol)...)
}
return lines
}
@ -841,7 +842,7 @@ func (tl TextList) toLines() []Line {
// only be called from toLines.
// Caller must sort the text list top-to-bottom, left-to-write (for orientation adjusted so
// that text is horizontal) before calling this function.
func (tl TextList) toLinesOrient() []Line {
func (tl TextList) toLinesOrient(tol float64) []Line {
tl.printTexts("toLines: before")
if len(tl) == 0 {
return []Line{}
@ -858,7 +859,7 @@ func (tl TextList) toLinesOrient() []Line {
lastEndX := 0.0 // lastEndX is tl[i-1].OrientedEnd.X
for _, t := range tl {
if t.OrientedStart.Y < y {
if t.OrientedStart.Y+tol < y {
if len(words) > 0 {
line := newLine(y, x, words)
if averageCharWidth.running {