pdf: Stretch words to fit in their boxes, for more perfect embedding

- Words are stretched to fit their boxes, which means the accuracy
  is now very high indeed. This was done by modifying gofpdf to add
  the SetCellStretchToFit function, which will hopefully be
  upstreamed in due course.
- Copy pasting from a PDF works well with lines rarely if ever being
  erroneously broken by the PDF reader. There was quite a bit of
  trial-and-error to improve this, and the stretched text plus a space
  being added after the word in CellFormat was the best (plus preserves
  accuracy of word and character locations).

3 files changed, 14 insertions, 7 deletions

diff --git a/go.mod b/go.mod
index 796618d..ec8afcc 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	github.com/aws/aws-sdk-go v1.40.6
-	github.com/phpdave11/gofpdf v1.4.2
+	github.com/nickjwhite/gofpdf v1.12.7-0.20210817123627-3cbaeb9797ef
 	github.com/wcharczuk/go-chart/v2 v2.1.0
 	golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d
 	rescribe.xyz/preproc v0.4.2
diff --git a/go.sum b/go.sum
index e802e09..45867e6 100644
--- a/go.sum
+++ b/go.sum
@@ -10,8 +10,8 @@ github.com/jmespath/go-jmespath v0.4.0/go.mod h1:T8mJZnbsbmF+m6zOOFylbeCJqk5+pHW
 github.com/jmespath/go-jmespath/internal/testify v1.5.1 h1:shLQSRRSCCPj3f2gpwzGwWFoC7ycTf1rcQZHOlsJ6N8=
 github.com/jmespath/go-jmespath/internal/testify v1.5.1/go.mod h1:L3OGu8Wl2/fWfCI6z80xFu9LTZmf1ZRjMHUOPmWr69U=
 github.com/jung-kurt/gofpdf v1.0.0/go.mod h1:7Id9E/uU8ce6rXgefFLlgrJj/GYY22cpxn+r32jIOes=
-github.com/phpdave11/gofpdf v1.4.2 h1:KPKiIbfwbvC/wOncwhrpRdXVj2CZTCFlw4wnoyjtHfQ=
-github.com/phpdave11/gofpdf v1.4.2/go.mod h1:zpO6xFn9yxo3YLyMvW8HcKWVdbNqgIfOOp2dXMnm1mY=
+github.com/nickjwhite/gofpdf v1.12.7-0.20210817123627-3cbaeb9797ef h1:Pq7OiIQ0gWrNQr12kRIvAH7qEr3i6hfSfd0smfwGgC0=
+github.com/nickjwhite/gofpdf v1.12.7-0.20210817123627-3cbaeb9797ef/go.mod h1:HHhz41M4FT6ogJi7KMknlu/sEJd6halot657/rJwzVM=
 github.com/phpdave11/gofpdi v1.0.12/go.mod h1:vBmVV0Do6hSBHC8uKUQ71JGW+ZGQq74llk/7bXwjDoI=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
diff --git a/pdf.go b/pdf.go
index be7f8a9..eb5f021 100644
--- a/pdf.go
+++ b/pdf.go
@@ -16,7 +16,8 @@ import (
 	"io/ioutil"
 	"os"
 
-	"github.com/phpdave11/gofpdf"
+	//"github.com/phpdave11/gofpdf"
+	"github.com/nickjwhite/gofpdf" // adds SetCellStretchToFit function
 	"golang.org/x/image/draw"
 	"rescribe.xyz/utils/pkg/hocr"
 )
@@ -112,7 +113,7 @@ func (p *Fpdf) AddPage(imgpath, hocrpath string, smaller bool) error {
 		if err != nil {
 			continue
 		}
-		lineheight := linecoords[3] - linecoords[1]
+		lineheight := pxToPt(linecoords[3] - linecoords[1])
 		for _, w := range l.Words {
 			coords, err := hocr.BoxCoords(w.Title)
 			if err != nil {
@@ -120,8 +121,14 @@ func (p *Fpdf) AddPage(imgpath, hocrpath string, smaller bool) error {
 			}
 			p.fpdf.SetXY(pxToPt(coords[0]), pxToPt(linecoords[1]))
 			p.fpdf.SetCellMargin(0)
-			p.fpdf.SetFontSize(pxToPt(lineheight))
-			p.fpdf.CellFormat(pxToPt(coords[2] - coords[0]), pxToPt(lineheight), html.UnescapeString(w.Text)+" ", "", 0, "T", false, 0, "")
+			p.fpdf.SetFontSize(lineheight)
+			cellW := pxToPt(coords[2] - coords[0])
+			cellText := html.UnescapeString(w.Text)
+			p.fpdf.SetCellStretchToFit(cellW, cellText)
+			// Adding a space after each word causes fewer line breaks to
+			// be erroneously inserted when copy pasting from the PDF, for
+			// some reason.
+			p.fpdf.CellFormat(cellW, lineheight, cellText + " ", "", 0, "T", false, 0, "")
 		}
 	}
 	return p.fpdf.Error()